Use Microsoft Authenticator on a new device
To change your authentication methods, browse to https://mysignins.microsoft.com/security-info and change the Default sign-in method to phone, or add the phone number for SMS MFA under +Add sign-in methods. Delete the MS Authenticator method which is already configured. Now go to +Add sign-in methods & set up your Authenticator App on a new device following the instructions.
On mobile -> open the Authenticator app on a new device, click on the + option on the top right side -> work and school account -> scan the QR code on the system.
Now you can change the Default sign-in method: to Authenticator App.
If you do not have access to the previous device or Microsoft Authenticator is malfunctioning on the previous device, please create a helpdesk ticket at https://helpdesk.brscia.edu.
Authenticator Troubleshooting: Troubleshoot problems using Microsoft Authenticator - Microsoft Support