Logging In problem with app

One of our group forgot his log in (or had never used the app). On line he created new login which was emailed and could log in to the website ok but the app would not accept it.
Any ideas? or should we just use another one of the groups log in/password?

Is he using the new app?

Yes, apparently. He had assistance from a more computer literate person. They also rebooted the phone.