Authenticator

Contact your organization’s IT help desk and ask them to require MFA re-registration for your work or school account, because you cannot approve the sign-in from the old phone and have no alternative verification method.

What to request

Send the help desk this message:

I replaced my phone and no longer have the old device. Microsoft Authenticator is my only registered verification method, so I cannot sign in. Please require MFA re-registration for my account so I can register Authenticator on my new phone.

An Authentication Administrator should:

1. Sign in to the Microsoft Entra admin center.
2. Go to Entra ID → Users.
3. Select your user account.
4. Select Authentication methods.
5. Select Require re-register MFA.

This removes the account’s registered phone numbers, Authenticator registrations, and software OATH tokens. At your next sign-in, you will be required to configure a new MFA method.^1^

Only your organization’s administrator can perform this reset; Microsoft Q&A participants cannot access or change your organization’s account.^2^

After IT completes the reset

1. Install Microsoft Authenticator on the new phone.
2. Sign in to your work or school account again.
3. When prompted to set up security information, choose Microsoft Authenticator.
4. Follow the displayed instructions and scan the QR code with the new phone.
5. Complete the test approval before closing the setup page.
6. If your organization permits it, register another backup method to prevent another lockout.

Restoring an Authenticator backup alone would not bypass this problem: for work or school accounts, only the account name is restored, and another sign-in is still required to complete setup.^3^

References

1. Manage user authentication methods for Microsoft Entra multifactor authentication
2. authenticator app issue after changing to a new phone - Microsoft Q&A
3. Transfer Microsoft Authenticator account entries to a new phone