Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Dear Backup9,
Good day! Thank you for reaching out to Microsoft community.
It seems like that you've lost access to the phone used for MFA, which is preventing you from logging into your Microsoft 365 admin console, and to resolve this, you’ll need to remove or reset MFA authentication.
However, there is another specific channel for your mentioned concern where you will get some possible information for certain specific resources and platform from our related community members.
I recommend visiting the dedicated Microsoft Authenticator community, which specializes in issues like recovering access when your MFA device is lost. They can offer specific guidance on resetting MFA or regaining access to your account.
I understand your concern but since your problem is related to Authenticator app, I would also like to suggest you post your concern in the related community i.e., Ask a question - Microsoft Authenticator - Microsoft Q&A to get the detailed help from the experts.
For more information, you may also check this MS article: Microsoft Authenticator FAQs - Microsoft Support.
Apologies for redirecting you to different community as the members in the category posted focus on the users with out of the box concerns on Microsoft 365 and have limited knowledge on the Microsoft Authenticator; so, to get the fast and better assistance, we have redirected you in the correct path.
Appreciate your patience and understanding. Have a great day!!
Best Regards,
S M Nazmun Nur