Hello @Maurizio Accardo ,
Thank you for reaching out to Microsoft Q&A.
I understand that you're facing an issue with Multi-Factor Authentication (MFA) using the Microsoft Authenticator app.
To resolve this issue, your account's MFA settings need to be revoked and reset. This action can only be performed by a Global Administrator (GA) in your tenant.
Steps for the Global Administrator to revoke MFA sessions and re-register for MFA:
- Sign in to the Azure portal.
- In the left menu, select Microsoft Entra ID> Users > All users.
- Choose your user account, then select Authentication methods.
- Select Revoke MFA sessions and then select Require re-registration MFA to reset the MFA settings for your account.
- So you will be prompted to register for Multi factor Authentication the next time you sign in.
Reference: Manage user authentication options.
Once the Global Administrator has reset your MFA, you should be able to proceed with registering the Microsoft Authenticator app successfully.
I hope this information is helpful. Please feel free to reach out if you have any further questions.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Thanks,
Chaithra.