Thank you for posting this in Microsoft Q&A.
In this situation you can contact any other Global Administrator of the tenant and ask them to perform "require re-register multifactor authentication" for your account.
Contact any other global admin of your tenant and ask them to perform below steps to reset your MFA so that you can re-register for authenticator app.
• Admin has to login to Azure portal and access Azure active directory.
• Once done they have to go to users blade on the left.
• Click on Authentication methods and click on “Require re-register multifactor authentication”.
• Now when you try to login to Azure services it will prompt you to register for MFA again.
If you are the only global admin on the account and are blocked entirely, you can reach out to the Azure Data Protection team to restore access. 866-807-5850
Also, for the future, you can create an emergency access account (break glass) in Azure AD. This account will help prevent being accidentally locked out of your Azure Active Directory (Azure AD) organization because you can't sign in for any reason.
https://docs.microsoft.com/en-us/azure/active-directory/roles/security-emergency-access
Some other support option include;
azcommunity@microsoft.com
or creating a ticket through a different account: https://learn.microsoft.com/en-us/microsoft-365/admin/get-help-support?view=o365-worldwide#phone-support
Let me know if you have any further questions on this.
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