I upgraded SuiteCRM from 8.5.0 to 8.9.1 to test the new release. Now I can’t log in with any account on the production instance, while the dev environment works with all accounts. The database is fine; new accounts are created correctly. Password recovery fails. I tested the fixes mentioned in these threads, without success:
basically, you can just copy a working user record from one 8.9.1 instance to another one.
So if you were to install a separate fresh 8.9.1 somewhere, create a 2nd user, make it admin and copy the users DB row over to your upgraded version, you’d be sure that at least the user record in the DB is correct.
Do you see any errors / issues during login attempts?
You can set the error log level to debug to get some more details in: public/legacy/config.php