Now we have a classmate who forgot his pw. I assigned him a temporary pw and now he can get into the site, however he says that he can't even view his own profile. It shows 'restricted' to joined classmates as if he hasn't joined. I have entered the site as if I were him (from my iPhone, ipad and pc) and I can get in fine and everything is normal. What can his problem be?

Browser cookies are required to verify that a classmate is logged in when they move from page to page on your website.

Tell him to make sure his browser supports cookies and that they are enabled.

See if that fixes the problem. Also ask him if any of the classmates on the Classmate Profiles page have a PADLOCK icon next to their name. If the PADLOCK is showing, he is not logged in to the website.