Can't join server?

My friend can’t join my server for some reason, he could before but now he can’t. He can join other servers. Everyone else who trys to join can. Can someone tell me whats wrong with his game?

Ask him if his problem is the same as mine (Here), if it is then maybe it’s something to do with an update or something out of our hands. Try getting him to try a clean install of GMod and post system specs if that doesn’t work, cheers.

Biggles, no offence, did you ever hear about port-forwarding?