Unable to log in to Microsoft Account due to lost authenticator app

Hi @yaaseen norton

Thank you for reaching out to the Microsoft Q&A Forum. 

I understand you're in a difficult situation, being unable to access your Microsoft account because the authenticator app was on a stolen phone. Reinstalling the app on a new phone won't work immediately because the new app isn't yet linked to your account. Please find below a few steps that may help resolve the issue: 

If you are still signed in to Office 365 on a browser: 

1. Go to: https://mysignins.microsoft.com/security-info 
2. Sign in with your Office 365 account. 
3. Under Security Info, remove the Microsoft Authenticator method. 
4. Add a new sign-in method (e.g., phone number, email, or reconfigure the Authenticator app). 

If you are locked out and cannot sign in, since your account is part of an organization, please contact your company’s IT administrator to request a Multi-Factor Authentication (MFA) reset. They will be able to assist you in regaining access to your account. To help them proceed, kindly ask your IT administrator to follow the steps outlined in the following Microsoft Learn article: Manage authentication methods for Microsoft Entra multifactor authentication - Microsoft Entra ID | Microsoft Learn 

If you are the only Global Administrator and you are completely locked out from the tenant. You may consider using the 24/7 support service available through Microsoft 365. You can initiate a support request by starting a free trial here:  Microsoft 365 Business Plans and Pricing | Microsoft 365

Assuming that you have already created an account after registering a free trial and you can go to Microsoft 365 admin center and click "Help & support" icon to raise your ticket. The agent will be able to create a ticket for you under the affected tenant and then transfer this ticket to Data Protection team who could help you to regain access.   You can follow this link for more instructions: Get support - Microsoft 365 admin | Microsoft Learn . With this solution, you might be able to regain access to your admin portal in the old tenant. This will allow you to reassign MFA to your current device.   

We hope the details provided will assist you effectively.

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I found this answer intuitively very helpful. I am encountering the same problem and am going to try this solution. I will let know here, if I am successful.