How to fix Office 356 and Outlook.com syncing error

Question

How to fix Office 356 and Outlook.com syncing error

Nick Douglas 0

Hello

Sorry for long message but this is hard to explain succinctly. I have a work calendar in an Office 365 account. I have to use this so colleagues can see my availability and book meetings with me. I also have a personal calendar on an Outlook.com account. Previously, I was able to 'pull in' the Outlook.com account appointments into my Office 365 account calendar. This is important to me because I keep personal appointments (medical appointments etc) in a seperate personal calendar and I mark them as 'Private'. This means colleagues can see when I'm unavailable due to a private appointment but not what the appointment is.

I came back from leave and my Outlook.com calendar had just vanished from my Office 365 calendar. I tried to re-add it going to Calendar-> Add calendar -> Add personal calendars -> Select personal account -> Selecting Outlook.com option. I got the following error message.

We're unable to complete your request

invalid_request: The provided value for the input parameter 'redirect_uri' is not valid. The expected value is a URI which matches a redirect URI registered for this client application.

I have tried numerous workarounds:

copying in an ICS link from the Outlook.com account to the Outlook 365 account
sharing the Outlook.com calendar with the Outlook 365 account
using Outlook desktop instead.

None of these worked for me. They either didn't sync properly or the events in the Outlook.com calendar only displayed to me on my Office 365 calendar as Private events, I couldn't see any of the details. On one hand, this is good, I want them marked as private when my colleagues see them but not when I do - no good if even I don't know what they are! If I use Outlook desktop, I can see both calendars in one view but the Outlook.com events don't sync with the Office 365 calendar so my colleagues can't see the private events at all. I even tried syncing a Gmail calendar instead and I couldn't get that to work either.

I have spoken with my IT department and they say they have made no changes that would stop this working and that this must have been something that MS have done. Potentially this is a nightmare where my collegues will book meetings with me when I am at the doctors! I don't want to have to keep a personal calendar and manually duplicate private appointments on my work calendar. I also don't want to just add my whole Outlook.com account to my Office 365 account because then that gives my employer access to my private emails as well. Microsoft Power Automate is apparently an option to duplicate calendar entries but beyond my skill-set.

This just worked before and it really shouldn't be this hard! Have MS done something to 'break' this feature? Can anyone please tell me what the error message garbage above means and how I can fix this? It's really simple, I just want to be able to keep my work and private appointments in two seperate calenders, see them in one view while my colleagues see private events as private. Many thanks for any help.

5 answers

Your answer

Answer 1

Dear Nick Douglas,

Thank you for reaching out to the Microsoft Q&A Community. I understand you're experiencing a frustrating syncing error between your Office 365 work calendar and your Outlook.com personal calendar. I'm happy to assist you with this issue.

The problem you've described—an error with redirect_uri when trying to add a personal calendar—is a known issue that can arise from changes to Microsoft's authentication and security protocols. Your IT department is correct that this is likely a change on Microsoft's end, not an issue with your settings.

The invalid_request: The provided value for the input parameter 'redirect_uri' is not valid error is a security message related to Microsoft's OAuth 2.0 authentication system.

OAuth 2.0: This is the protocol that allows one application (in this case, your work Outlook calendar) to access a resource (your personal Outlook.com calendar) without you having to share your personal password.

Redirect URI: This is a pre-registered URL that tells Microsoft where to send you back after you've successfully authenticated your personal account.

The error means that the redirect URI being used by your work Outlook calendar to authenticate your personal Outlook.com account is either incorrect or no longer registered in Microsoft's system. This is a security measure to prevent a third party from intercepting your authentication token.

The fact that this feature worked before and now produces this error strongly suggests that a recent update to Outlook's web app or the underlying authentication service has inadvertently broken this specific integration.

While there is no direct "fix" for the redirect_uri error on the user end, there is a reliable workaround that provides the exact functionality you need: in-app calendar sharing.

This method bypasses the broken "Add personal calendars" feature and uses a different, more stable protocol to achieve the same result. It is a supported and documented feature of Outlook.com and Office 365.

Please follow these steps to fix the issue:

Step 1: Share Your Outlook.com Calendar

a. Sign in to your personal Outlook.com account on the web.

b. Go to the Calendar and select the calendar you want to share (e.g., "Calendar" or "Personal").

c. Click the Share button at the top of the calendar view.

d. In the sharing menu, enter your Office 365 work email address and press Enter.

e. Set the permission level to "Can view all details" or "Can view titles and locations". This is crucial for you to see your private appointments.

Note: The events will be marked as "Private" on your personal calendar, so even with this permission level, your colleagues will only see that you are "Busy" when they check your availability. You, however, will be able to see the details.

Step 2: Accept the Shared Calendar in Your Office 365 Account

a. Open your Office 365 work email inbox.

You should have received an email with the subject "You're invited to share [Your Name]'s calendar."

b. Click the Accept button within this email.

Step 3: View the Calendars in Overlay Mode

This will allow you to see both your work and personal appointments in a single, combined view, just as you want.

a. In your Office 365 work calendar, find your newly added personal calendar in the left-hand navigation pane.

b. Hover over the name of the personal calendar and click the three dots (...).

Select Overlay. This will merge the two calendars into a single view.

You can see all your appointments in one place, your colleagues can see when you are busy but not the details of your private appointments, and you don't have to manually duplicate events.

For more information, you can refer to the official Microsoft documentation on sharing calendars:

Share your calendar in Outlook on the web - Microsoft Support

Show personal events on your work or school calendar

I hope these steps help you resolve the problem. If you require additional guidance, feel free to reply to this thread, and I’ll be happy to assist you.

Warm Regards,

Alice

Microsoft Q&A Support Specialist

Answer 2

Alice-N 1,110 Microsoft External Staff Moderator

Good day! I hope you're doing well!

It has been a while and I am writing to see how things are going with your issue. Have you had a chance to check the reply provided? Are you encountering any difficulties following the steps ? Please feel free to let me know if there’s anything I can assist you with.

Warm Regards,

Alice

Microsoft Q&A Support Specialist

Nick Douglas 0 Reputation points

2025-08-06T14:36:25.4066667+00:00
Hi Alice

Many thanks for the detailed reply - much appreciated. I followed the instructions to share my outlook.com calendar with the Office 365 account. I'm still having problems:

The outlook.com events display for me also as private in my Office 365 calendar. I can't see the event details or edit them. This is despite the fact that I set permissions to 'Can Edit' when sharing. I had this problem when I tried sharing before. Some searching indicated that this is because I mark all events in my outlook.com calendar as 'Private' and this is overiding the instruction to allow me to view/edit from my Office 365 account. But if I don't mark them as 'Private' then surely my colleagues would be able to see all the outlook.com event details when viewing my Office 365 calendar, which I don't want?

But, it's a moot point at the moment because the outlook.com events don't show up at all for my colleagues when viewing my Office 365 calendar. I think the reason for this is that when sharing, Outlook treats them as two seperate calendars - yes I can see them together in overlay view but they aren't actually merged as such, just viewable on a combined view, which is why my colleagues can't see them. Is that correct?

What I need is for the oulook.com events to be viewable/editable by me in my Office 365 calendar but display as 'Private' when my colleagues look in my calendar to schedule an appointment.

Also, as you helpfully explain, the problem has been caused by changes MS have made. While an effective workaround would be great, and I'll take what I can get, it would be better if they 'fixed what they broke'. How can I alert whoever can fix it about the problem please? Can you please advise further?

Many thanks

Nick.

Answer 3

Dear Nick Douglas ,

Thank you for your update. Thank you for your patience and coordination. I am very sorry that the problem has not been resolved.

We understand that you are using an Office 365 enterprise account and that this functionality previously worked as expected. Our standard procedure is to escalate the issue to Microsoft Commercial Support for further investigation. You can initiate a support request via the following channels:

In parallel, your requirements can be fulfilled using Microsoft Power Automate, which offers professional-grade tools for managing calendar events and permissions. Here's how to get started:

Steps to Use Power Automate for Calendar Permissions

a. Sign in to Power Automate Go to the Microsoft Power Automate | Home and sign in with your Office 365 account.

b. Create a New Flow Choose “Create” from the left navigation pane and select either:

Automated cloud flow (triggered by an event)

Scheduled cloud flow (runs at set intervals)

c. Add Calendar Actions Use connectors like “Outlook” or “Office 365 Outlook” to:

Create calendar events
Set visibility to “Private”
Sync events between calendars

d. Customize with Conditions and Variables Add logic to control which events are synced and how they appear. You can use variables to dynamically set privacy flags or filter based on event type.

e. Test and Deploy Save and test your flow. Once validated, you can share it with your team or deploy it across your organization.

For tutorials and examples please refer to these links :

a. Power Automate Tutorials [Beginners + Advanced] - SPGuides.com

b. Explore the Power Automate home page - Power Automate | Microsoft Learn

c. How to Use Power Automate Workflows [Tutorial Guide for Beginners]

Disclaimer : Microsoft is providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above links.

If the issue persists, we also recommend testing with a newly registered personal Outlook.com account to help determine whether the problem is account-specific or systemic.

If you still have any problems, please don’t hesitate to provide further information and I am here to help you resolve the problem.

Warm Regards

Alice

Microsoft Q&A Support Specialist

Nick Douglas 0 Reputation points

2025-08-07T10:57:12.75+00:00

Hi Alice

Thanks again for the detailed reply. Before posting my query, I did try to get this working with Power Automate and honestly spent hours on it. Firstly, it's just beyond the level of capability of most ordinary users I think. The problem I had was that I was required to set a beginning and end field. The default tools added a time zone, which meant the flow kept failing. I tried using the AI help and it just created an endless trail of 'solutions' that didn't work, causing the AI to try to fix the last failed solution so that the original problem was never solved. Honestly, I think most users would have been too daunted to even try to use this tool and definitely given up quite quickly. As I say, I spent hours and eventually had to give up in frustration. Is there a video that MS has perhaps that shows how to set up this specific flow since it's a known flaw that MS changes have caused? To be honest though, I'm really not optimistic, I just don't think that Power Automate is usuable by average users. Is there anything else I can try?

Thanks again

Nick.

Answer 4

Hi Alice

Thanks again for the reply. Wow I'm having the worst time with MS products. I posted a lengthy reply here earlier about my experience with Power Automate and it's totally disappeared! Just gone! Guess I'll never get that time back!

The short version is that I tried Power Automate before I posted my question and it was hopeless. I literally spent hours trying make it work. The skills needed are just way beyond what can be expected of an ordinary consumer user. The issue was my flow wouldn't work because I needed to set some dates/times in a field. The auto-populated options had a time zone in them which broke the flows. I tried to get the AI to help me fix it but was just an endless stream of failed attempts where the AI tried the fix the fixes that didn't work. I've just tried tried it again. Same problem. Just to show I'm not making it up how complicated PA is for an ordinary user, here's an example of an error message I'm getting.

"Flow save failed with code 'OpenApiOperationParameterValidationFailed' and message 'Input parameter 'item' validation failed in workflow operation 'Update_event': The parameter with value '"@triggerOutputs()?['body/start']"' in path 'item/start' with type/format 'String/date-time' is not convertible to type/format 'String/date-no-tz'.'."

I really shouldn't have to be an amateur software engineer and waste hours trying to fix MS rubbish software just to sync a couple of calendars. If I had the slightest choice I would run as away from all this MS garbage as far as I could. Unfortnately, it's what my employer uses for calendar management so I'm stuck with it. I realise that you are being helpful and hanging in there with suggestions but I think the only option is that MS has to fix it. Is there any realistic chance of anything I might do bringing this about? Is there anything else I can try to make it work? Thanks again for your help.

Stefan Blom 310.3K Reputation points MVP Volunteer Moderator

2025-08-07T18:05:08.9033333+00:00

I posted a lengthy reply here earlier about my experience with Power Automate and it's totally disappeared! Just gone! Guess I'll never get that time back!

Side-note: Usually, you can find your other threads if you click your avatar at the top of the forums page and then click the link for Settings.

Note that for more specific assistance with Power Automate, you may want to ask your question at https://community.powerplatform.com/ .

Answer 5

Nick Douglas 0

Hi Stefan

Thanks for the reply and suggestions. I honestly have spent hours trying to get the Power Automate solutions to work and given up. It's really not designed for ordinary users and I don't have time to become a software engineer. I'm still hoping for a solution for us 'mere mortals'. Any suggestions much appreciated.

Many thanks.

Stefan Blom 310.3K Reputation points MVP Volunteer Moderator

2025-08-07T18:31:45.95+00:00

Sorry, I am not the right person to give advice on Power Automate.
Nick Douglas 0 Reputation points

2025-08-07T19:06:45.5133333+00:00

Hi Stefan

Ok thanks, that's fine because it doesn't work anyway. Can you help with any other suggestions please?

Thanks.
Alice-N 1,110 Reputation points Microsoft External Staff Moderator

2025-08-13T04:41:56.8366667+00:00
Dear Nick Douglas,

Thank you for your update. Thank you for your patience and coordination. I am very sorry that the problem has not been resolved. Sorry for that I didn’t come in a timely manner.

I understand your frustration with the technical complexity of Power Automate and the fact that a previously working feature is now broken. You are absolutely right that this should not require an extensive, manual workaround for a basic function. I apologize that the suggestions so far have not provided a simple and effective solution.

Based on your detailed feedback, the core issue remains that you need a way to have your personal, private appointments show up as "Busy" on your work calendar without exposing the details, and the native calendar sharing isn't working as intended for this specific use case. The "invalid_request" error you first encountered and the subsequent issues with calendar sharing strongly suggest an underlying systemic problem that needs to be addressed by Microsoft.

Since Power Automate is not a viable solution for you, let's focus on a different approach that might be more manageable.

While not a perfect fix, the following method offers the closest manual alternative to the functionality you lost, and it doesn't require any advanced technical skills.

Create a separate calendar in your Office 365 account.   a. Go to your Office 365 calendar.   b. On the left-hand side, click "Add calendar."   c. Select "Create new calendar" and give it a name like "Personal Appointments."

Manually duplicate your private appointments.   a. When you create a new private appointment in your personal Outlook.com calendar, also create a corresponding, separate appointment in your new "Personal Appointments" calendar within Office 365.   b. For the Office 365 appointment, set the title to something generic like "Private Appointment" or simply "Busy."   c. Mark this event as Private in your Office 365 calendar. This ensures that your colleagues will only see that you are busy during that time, but they won't see the details.

This method completely bypasses all the sharing and syncing issues and provides you with the exact outcome you need: your colleagues see you as busy, but they can't see the details, and you have a clear separation between your work and personal calendars.

Reporting the Problem to Microsoft

You asked how to alert Microsoft about this issue. The best way to get this is to submit feedback directly.

Submit Feedback via Outlook:   a. In Outlook for the web , click the ? icon in the top-right corner.   b. Select Feedback.   c. Describe the issue you're facing, referencing the invalid_request: The provided value for the input parameter 'redirect_uri' is not valid error and explaining that the "Add personal calendars" feature is broken. Be sure to mention that the calendar sharing workaround also fails to provide the full functionality you need.

Contact Microsoft Commercial Support:   a. As a user with an Office 365 enterprise account, your IT department has access to a dedicated support channel. Encourage them to open a support ticket on your behalf, providing them with all the details you've shared. This is often the most effective way to get an issue officially investigated and escalated.

I understand this is not the simple, technical fix you were hoping for, and I apologize again for the inconvenience. The manual workaround ensures your colleagues don't book meetings over your private time while we hope Microsoft addresses the root cause of the syncing error.

If you still have any problems, please don’t hesitate to provide further information and I am here to help you resolve the problem.

Warm Regards,

Alice

Microsoft Q&A Support Specialist
Nick Douglas 0 Reputation points

2025-08-13T12:04:28.5266667+00:00

Hi Alice

Thanks for the reply. I have gone back to my IT department for help. I don't want to manually duplicate the entries as, apart from the additional effort, I'm bound to forget or make a mistake in the duplication, which will lead to confusion and diary mess. Can I ask that you please escalate the problem to the channels available to you? It seems that you have an understanding of why the original process is broken and so it makes sense for you to explain this to whoever can fix it. You will also know how to reach the right people more efficiently.

Many thanks.

Nick.
Alice-N 1,110 Reputation points Microsoft External Staff Moderator

2025-08-15T10:12:04.2466667+00:00

Dear Nick,

Thank you for your update, and for your patience and cooperation. I’m very sorry that the issue remains unresolved.

I completely understand your frustration. The error you're encountering with Power Automate confirms that this is a technical issue requiring a more advanced solution than a simple workaround. It’s not something an end user should be expected to troubleshoot. Since the standard syncing methods are failing and the Power Automate solution is proving overly complex, I’ve identified a direct and effective alternative that is often overlooked.

This method involves sharing your calendar via an iCal link and adding it to your Office 365 calendar. It’s a reliable way to sync calendars and bypass the OAuth redirect URI error. The key is to correctly configure the sharing permissions on your Outlook.com calendar before generating the link. This ensures you can view all details of your private appointments, while your colleagues will only see that you’re busy.

Please try this workaround and let me know if it helps.

Solution: Share and Sync Your Calendar with an iCal Link

This provides a one-way sync from your personal Outlook.com calendar to your Office 365 calendar. Any changes made in your Outlook.com calendar will automatically reflect in your work calendar.

Step 1: Set Permissions on Your Outlook.com Calendar

a. Sign in to your personal Outlook.com account on the web.

b. Go to Calendar.

c. In the top-right corner, click the Settings gear icon.

d. Select View all Outlook settings at the bottom of the menu.

e. In the left-hand pane, select Calendar, then Shared calendars.

f. Under Publish a calendar, choose the calendar you want to share.

g. For permissions, select Can view all details.

h. Click Publish.

By setting permissions to "Can view all details," you ensure that anyone with the link can see full event details. When you import this calendar into your work account, you’ll see all details—even for events marked as Private. Your colleagues will still only see the "Private" status when checking your availability via Office 365, as that’s the default for external calendars.

Step 2: Get the iCal Link

a. After publishing, both an HTML link and an ICS link will appear.

b. Copy the ICS link—this is the one you’ll use to subscribe to the calendar in Office 365. It’s a long URL ending in ".ics".

Step 3: Add the iCal Link to Your Office 365 Calendar

a. Sign in to your Office 365 account on the web.

b. Go to Calendar.

c. In the left-hand pane, click Add calendar.

d. Select Subscribe from web.

e. Paste the ICS link into the URL field.

f. Name the calendar (e.g., "Personal" or "Outlook.com") and choose a color/icon if desired.

g. Click Import.

This will add your personal calendar to your Office 365 account. Events will appear in a separate color, and you’ll be able to view all appointment details. This method is highly effective because it doesn’t rely on the broken "Add personal calendars" feature. It uses a standard calendar-sharing protocol that’s less vulnerable to internal system changes.

Once again, I sincerely apologize for the inconvenience you've experienced while using our product. I understand how deeply this has affected you. If you continue to encounter issues, please don’t hesitate to provide more details—I’m here to help resolve the problem.

If you found this answer helpful, we’d greatly appreciate it if you could click "Accept Answer" and kindly give it an upvote. Your feedback helps others in the community as well.

Warm regards,

Alice

Microsoft Q&A Support Specialist
Nick Douglas 0 Reputation points

2025-08-19T14:49:15.1933333+00:00

Hello

Thanks again for the reply. I tried to use the suggested workaround and to my complete and unparalleled delight, the original way to add a personal calendar has been fixed! I cannot convey my utter joy at this fact! Ok, so now I'd like to understand how it got fixed so if it gets broken again I know what to do. I know that it had to be fixed by MS (not my IT department) but can you please advise on what happened to alert them to the problem and fix it? Is there a way I can do this going forward that will be quick and effective? Thanks again for all your help with this.

Best wishes

Nick.
Alice-N 1,110 Reputation points Microsoft External Staff Moderator

2025-08-21T08:55:53.9666667+00:00
Dear Nick,

Thank you for your update. I appreciate your patience and coordination throughout this issue. I am very glad to hear that the calendar integration has been restored and that you are once again able to add your personal calendar as intended.

To address your question regarding how the issue was resolved and how to respond effectively if it occurs again, please find below a clear and structured approach:

Step 1: Sign in to the Microsoft 365 Admin Center

a. Visit the official Microsoft 365 Admin Center: https://admin.microsoft.com/AdminPortal/Home#/servicehealth

b. Sign in using your Microsoft 365 administrator credentials.

If you do not have admin access, please contact your IT department for assistance.

Step 2: Access the Service Health Dashboard Once signed in:

a. Navigate to Health > Service Health in the left-hand menu.

b. This dashboard displays current and historical incidents affecting Microsoft 365 services, including Outlook and calendar functionality.

Step 3: Review Relevant Incidents

a. Look for any incidents or advisories related to Exchange Online, Outlook.com, or Calendar services.

b. Click on any listed item to view detailed information, including:

A summary of the issue

Affected services and regions

Status updates and resolution timelines

Step 4: Subscribe to Service Health Notifications

a. In the Service Health Dashboard, configure notification preferences:

b. Select Preferences or Health Alerts

c. Choose to receive email notifications for incidents affecting specific services

This will ensure you are promptly informed of any future disruptions.

Step 5: Report a New Issue (If Not Listed)

If your issue is not reflected in the dashboard:

a. Go to Support > New service request

b. Provide a detailed description of the calendar integration problem

Attach relevant screenshots and error messages (e.g., redirect URI error) Microsoft support will investigate and respond accordingly.

Step 6: Document Your Configuration

Maintain a record of your calendar setup, including:

Account types used (e.g., Outlook.com and Office 365)

Permissions granted

Integration method (e.g., Add calendar > Personal calendar)

This will help you replicate the setup or explain it clearly to support staff if needed.

If you still have any problems, please don’t hesitate to provide further information and I am here to help you resolve the issue. If you found the answer helpful, we’d really appreciate it if you could click "Accept Answer" and kindly give it an upvote. Your feedback helps others in the community too!

Warm Regards,

Alice

Microsoft Q&A Support Specialist

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How to fix Office 356 and Outlook.com syncing error

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