Hello, thank you for reaching out to Microsoft Q&A.
Could you please confirm whether you have deleted the Microsoft Authenticator app or switched to a new mobile device?
If you no longer have access to the Authenticator app, follow this method to sign in to your account or to add your account back into the Authenticator app.
- Install the Authenticator app on your new/same device.
- If you have a recovery/backup email account where you backed up all of your authenticator credentials previously on your old device, you can use that account during sign-in by selecting Begin recovery on the first screen of the Authenticator app.
- During sign-in, you will be asked to verify your identity using the Authenticator app. The sign-in prompt does not know you are using a new device; it just thinks you’re signing in to a device. Since you can’t verify it with the Authenticator app, select “I can’t use my Authenticator app right now.”
- You will then be asked to verify your identity using alternate security contact methods such as your phone number or email address.
- For security reasons, you will be asked to reset your password.
- Follow the same procedure and add your account to the Authenticator app again.