I got notified today, that someone couldn’t join my server (Hes the first one getting this error, others can play fine). When he tries to join the server he keeps being stuck in the loadingscreen, saying ‘Authenticating with Steam’, He is using a legit gmod version, I told him to validate the files, dont know yet if that helped, when I tried to google it, I saw many people getting this error recently, and someone said joining manually over Steam -> Servers helps, and some even reinstalled their game.
Edit: Now I’m getting this error too.
Edit 2: Only 1 person can join, if a 2nd person tries to join, that person gets the error.
Heres a screenshot –
[editline]3rd April 2016[/editline]
Alright it seems to work for now after a server restart, dunno if it stays like that, since it worked fine 2 days ago.