"Your account is inactive. Contact your administrator to activate it."
If I "sync" the user directory, the user becomes active again and I proceed to log him in with the same ticket without error.
But it is annoying that i need to sync user directory so often.
The documentation indicates that if the user was removed from the source database, it may block or inactivate the user for security reasons but my users still exist in the db. Link : Inactivating users ‒ Qlik Sense
Yes, this was because of a bug in Custom ODBC. If your user and attribute tables contain upper case values in userid field, it throws error and inactivates users. Changing userid field data into lower case solved the issue.