I can't log in using Microsoft Authentication.

Dear @psbiogas,

Good day. Thank you for posting your question in the Microsoft Q&A forum!

I’m very sorry for the inconvenience you’ve experienced, based on the details you shared.

If you are using a work/school account, I would recommend you contact your IT Admin to reset your MFA settings through the Microsoft Entra Admin Center. Ask your administrator to follow these steps:   

1. Sign in to the entra.microsoft.com as at least one Authentication Administrator. 
2. Select User > All user.  Select the user (your account) to act on and select Authentication methods then select Require re-register of multi-factor authentication.  

Require re-register MFA:  This disables all previous authentication methods. You'll then be prompted to configure a new MFA authentication method the next time you try to sign in, so you can set up from the start and add a new authenticator app.  

For step-by-step details, see the official Microsoft documentation: Manage authentication methods for Microsoft Entra multi-factor authentication - Microsoft Entra ID | Microsoft Learn    

If you’re unsure who the Global Admin is within your school account's organization, you can find guidance on locating them here:  How do I find my Microsoft 365 admin? - Microsoft Support  

Note: Once re-registration is triggered, all your existing MFA methods such as phone numbers, Authenticator app, or other verification options will be removed. You will need to set up new MFA methods during your next login. Please ensure you have access to a valid phone number or the Microsoft Authenticator app before attempting to sign in again. 

Please feel free to contact me if you are an admin. I appreciate your patience, and I am here to help. Looking forward to your response!

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

If you are unable to log into your business account because you can't authenticate through the Microsoft Authenticator app, there are a few steps you can take to regain access:

1. Contact Microsoft Data Protection Support: Since you are the sole administrator of your account, you will need to contact Microsoft support directly. You can do this by calling their customer service hotline. When you call, explain that you are locked out of your account and that you need assistance with resetting your authentication method.
2. Follow the IVR Prompts: When you call, you may go through an automated system. Be prepared to respond to prompts indicating that you are a business user, that you are the administrator, and that there are no other administrators in your organization. This will help direct you to the right support team.
3. Create a Trial Tenant: If you are unable to reach a support agent, consider creating a new trial Microsoft 365 tenant. This will allow you to access the Admin Center and submit a support ticket requesting help for your locked account. Make sure to cancel the trial once your issue is resolved to avoid any charges.
4. Alternative Authentication Methods: If you have set up alternative authentication methods (like SMS), try using those to log in. If not, you will need to rely on contacting support for assistance.

These steps should help you regain access to your account. If you need further assistance, don't hesitate to reach out to Microsoft support again.

References:

• I can't log in to my business account because it is requiring Authenticator app which I do not have - Microsoft Q&A
• Microsoft authenticator sending me into a spiral - Microsoft Q&A