A paying user on my website is unable to access our service, getting the error "Authentication problem, please contact website administator" when they try to login. I have tried logging in as them myself and get the same error. However, if I click "login as user" in the admin panel it works fine. This probably needs some support from an aMember developer because I can't find any concrete clues yet and don't want to leave a paying user hanging whilst I figure it out. I have looked at the error logs and there is no record, I have looked at access logs and it shows the user as logging in... We have tried resetting the password and rebuilding the core and third-party databases, none of this has changed the outcome.