Error: "This Steam account does not own this game. Please log into the correct account."
I need some help on this. I have recently downloaded Garry's Mod 9.0.4 since I can't buy GMod 10/11 yet. I installed, changed the GameInfoID to 215, and restarted Steam. I launched it sucessfully, able to play Single-Player mode. But when I went into Multiplayer mode, I couldn't join any servers due to this error:
"ERROR: This Steam account does not own this game. Please log into the correct account."
I cannot join any servers at all EXCEPT one of the FaceWAN Freebuild servers (Which I forgot the name of). I can't even create my own server. Me and my friend are having this problem, and we can't join any servers that have auctal players on it. I would like REAL help, and NOT stupid "Go buy Gmod 10/11" posts please.