@ejnarDK Like you, I'm sceptical. Without knowing his location and error messages it would be impossible to even suggest viable solutions.
If it is a case of a government restricting access then anything I would suggest won't work, but I'll suggest one thing if you can't get more information. Can he create a new account and log in with that after logging in on the previous day with the 'difficult' account?
One work around if it is in fact the case he can't log in because of restrictions could be to send out a substitution. Not ideal!