How to restore access for admin user to a development entra ID directory when the MFA is not working anymore after setting up a new iPhone

I have a main directory we use in PROD and a development directory for our internal dev and test environment. The same admin user is used for both directories. I'm using the MS authenticator app for MFA. Accessing the main directory still works but I cannot access anymore the dev directory. I always get an error when entering the code and the pop up in the auth app doesn't display. I assume I lost the account in the auth app when setting up my new iPhone (in general I had many such issues with all the different MS accounts in the auth app!). Currently I don't know how to restore the account in the auth app nor how to access the dev directory. The test user can still access the dev directory but they only have read-only access and cannot fix the problem.