Microsoft authenticator got deleted and now can't log into my son's minecraft account

Question

I'm having the same issue as in this thread but after some seach I didn't find any solutions. I'm trying to call the microsoft support (800) 865-9408 but all get denied or directed to online support website which didn't help at all.

Basically my son's account is ending in .onmicrosoft.com domain, I've reset the password but it's still asking for Authenticator app's number, when I select I can't use the app there is another option saying to receive authentication code which is still from Authenticator app, the workflow is so poorly designed and there is solution. I tried to recover the account through the email or phone but it said the they all not associated with any microsoft account. But I used that email for the password reset, how come it's not associated. I need a human help me with this, can provide more detail on the account. We have to use it for one of his classes, it's super urgent, please take a look!