One of my users suddenly cant log in to the app

I have deployed about 16 apps and ALL use provider - Microsoft.

After the Holiday break one of my users cannot log back in. It seems to default him to Gmail. Then when he puts in his Microsoft credentials - it says his password is wrong - (we verified it was right). I have tried deleting the app off his phone and checked for phone updates (android and all updates are done).

Still no luck.

Anyone having this issue?
What is the solution?

I want to also ask - while on this subject - can i force Microsoft login even when i use Google sheets as my data table?

@Tiger

Does this affect security at all? Meaning - should i stick with only one source provider?

@Tiger
This has nothing to do with the security…This is about the authentication providers you allow…

ok. Thanks