You will have to re-download it again to your mobile device, and if you had configured it for a backup (To Google Drive OR iCloud ), you should be able to restore yourself.  Otherwise, you will need to goto the Microsoft MFA Website Setup ( https://aka.ms/mfasetup ) and re-add in your authenticator.

You can also sign in, if needed, via the other method you setup, being your mobile number via Text Message or your work direct extension number.