Not really sure but perhaps you could see if he can log into an alternate account on his computer and see if that works? Like let him log into your account if you have one or he could make a new account just to see if it's somehow his computer, which would be weird.. Or if it's his account. If he can user other accounts just fine, that will tell you it's something wrong with his specific account.

Then if that's the case.. I guess you either try to look through your settings and see if things have been shut off or disabled, and then perhaps try to contact Facebook, which I'm not sure how difficult that is.. But you could also try googling the problem and seeing if you can find similar experiences with others on there. That might help! Good luck!