I need to setup my authenticator app again to be able to sign in

To regain access when the Microsoft Authenticator app is the only sign-in method and the phone has been changed, the account’s MFA settings must be reset by an administrator or by Microsoft support.

Since this is a business/partner account and the only available method is the Authenticator app (no working SMS or alternate method), the following options apply:

1. If there is another administrator in the organization
   • Ask that admin to reset multifactor authentication (MFA) for the account in Microsoft Entra ID:
     • Go to Microsoft Entra admin center (https://entra.microsoft.com).
     • Navigate to Users → All users and select the user account.
     • Open Authentication methods.
     • Choose Require re-register multifactor authentication.
   • After this reset, sign in again; the portal will prompt to set up Microsoft Authenticator from scratch using a new QR code.
2. If this is the only administrator account for the tenant
   • The Microsoft Data Protection team must be involved to verify identity and reset access:
     • Call Microsoft support using the appropriate Customer service phone numbers - Microsoft Support entry.
     • When the automated system asks for the problem, state that the issue is with Authenticator for an Office 365 for business/company account.
     • Confirm that this is an administrator account and that there are no other admins.
     • Ask the agent to open a service request and route it to the Data Protection team to reset MFA and restore access to the admin account.
   • Be prepared to provide:
     • The administrator email address.
     • The tenant domain.
     • Error messages seen when trying to sign in.
     • Confirmation that this is the only admin account.
3. If the subscription is through a partner/reseller
   • Contact the reseller’s support and ask them to open a Microsoft support ticket on behalf of the tenant, explaining that the only global admin is locked out due to Authenticator and needs MFA reset by the Data Protection team.
4. After Microsoft resets MFA
   • Sign in to the account again.
   • When prompted for more information, set up the Microsoft Authenticator app on the new phone:
     • Install the app.
     • Sign in to the service (for example, Microsoft 365 or Partner Center) with username and password.
     • Follow the prompts to scan the QR code and complete registration.

This process is required because forum moderators and tools cannot bypass or change MFA for an admin account; only another admin or Microsoft’s support/Data Protection team can do it.

References:

• I have a Micrsoft business account and I am the admin and the only user registered under this account. I can't log in because i have replaced my phone and the authenticator doesn't work. - Microsoft Q&A
• Microsoft authenticator sending me into a spiral - Microsoft Q&A
• Use a screen reader to set up and troubleshoot multifactor authentication
• Common problems with two-step verification for a work or school account