Unable to use office365 despite the fact that Our University has a collective subscription

Dear @Muyanja Ssenyonga Jameaba,
Thank you for contacting Microsoft Q&A!

I appreciate your efforts in reinstalling Office and seeking help from your university technicians. I understand your situation, firstly, please help me check:

1. Try Signing In via Web Browser Visit https://www.office.com and attempt to sign in using your university credentials. If successful, the issue may be isolated to the desktop application.
2. Use a Different Device Try signing in on another device (e.g., a phone or another computer) to determine if the issue is device-specific.
3. Verify System Time and Date Ensure your device’s time and date settings are accurate. Incorrect settings can interfere with authentication.
4. Check for Windows Updates Make sure your operating system is fully updated. Office apps rely on system components that are patched via Windows Update.
5. Review Proxy or VPN Settings Disable any VPN or proxy temporarily to see if Office apps are misinterpreting the network configuration.
6. Are other students or staff members experiencing the same error? Is this potentially related to a network or proxy configuration on the university’s system?

Next, based on your description, please try my suggestion steps bellow to reset the sign in data:

1. Repair the Office Installation
   Go to Control Panel > Programs > Programs and Features, right-click on Microsoft Office, select Change, and choose Online Repair.
   Detailed instructions: Repair Office Application
2. Sign Out & Close Applications: Completely sign out of your education account in all Office app (like Word or Excel). Ensure all these applications are fully closed.
3. Disconnect Education Account: Go to Windows Settings > Accounts > Access work or school. If your organization's account is listed, select it and choose Disconnect. Restart your PC if prompted. For example (your Disconnect button will blue, not grey like my environment test):
   
4. Clear Windows Credentials:
   In the Windows search bar, type Credential Manager and open it. Go to Windows Credentials.
   In the Generic Credentials section, remove any credentials related to Office, Outlook, Teams, or Microsoft Office.
   In the Web Credentials section, clear the cached credentials for Microsoft-related accounts.
   For more details, please check this reference: Credential Manager in Windows - Microsoft Support

Also, about the error internet connection 2603, I found a case similar maybe you can try to follow based on this reference: 

• Access the Internet Options in your Control Panel. 
• On the Windows taskbar, type Control Panel in the Type here to search box, and select Control Panel in the search results. 
• In the Control Panel window, select Network and Internet, and then select Internet Options. 
• In the Internet Properties window, select the Advanced tab, and then click Restore advanced settings.  I hope this helps! Note: 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 link

If the issue persists after all workaround above, please send me screenshot of your error. Any insights or updates would be greatly appreciated.

Please note that our initial response may not resolve the issue immediately. However, with your collaboration and more detailed information, we can work together to identify the best solution.

If you need further assistance, please let me know.

Best Regards.

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From your description, unable to reach Microsoft services even when you have a active connection to the internet, with the error reported as there is no internet connection - this seem to point to a few possibilities.

To further clarify the problem -

1. Is the problem isolated to you, or the entire university is facing the same problem?
2. Does the problem happen if you try to connect outside of the university wifi? For example a when you are home, or using a mobile phone as a hotspot?
3. Is the problem the Office app, or you are also unable to logon to Microsoft365 via a browser?

If the answer to question 1 is everyone is facing the same problem, then likelihood is there is something blocking anyone using the university network from reaching Microsoft servers. Usually a security setting in one of their security devices.

If the answer to question 1 is only you are facing the problem, and no one else, then we need to further isolate whether its university network related, in which case we go to question 2, if you bypass the university network whether it will still work, meaning trying it at home, or using a different internet service say outside at a starbucks.

If it still doesn't work, and it's only you, and it doesn't work regardless of what network you are on, and it works if you are using a different device (like your friend's machine) then we can safely isolate it to your machine.

If on your machine, you can login to Microsoft365 using a web browser - say https://www.office.com/, but your Office app doesn't work, then we isolate it to your app. If it doesn't work regardless web or office app, then it might lead to some software on your laptop is preventing you reaching Microsoft servers. Then the question would be what changed in the last 48 hours before the problem happened. Did you install some new anti-virus software? or any software? Did you change some settings on your windows firewall?

Perhaps give us some feedback on what you, or they have tried, or have told you, so we can figure this out further.

Please also share your machine specifications, OS, Antivirus if any etc and describe your troubleshooting in some detail for us to get a clearer picture.

Thank you