My two friends and I are having problems inviting each other to game lobbies. Basically, I can invite friend A, and friend B can invite friend A, but I don't see invites from either of them, and neither does friend B. I received this game as a gift over Steam, and I had the problem where it wasn't listed in my game's list, so I had to install it via the run command and typing steam://install/104700. Friend B also installed the game this way. Does anyone think this could be the problem? If not, what could it be?
The matchmaking system was overhauled recently. There are bugs that sometimes prevent players from showing up in chat lobbies or friend lists so that you can invite them to team up with you. A current workaround is to have your friend restart SMNC until he shows up in the lobby or your friend list, until the bugs are addressed.