I have the same problem. I played with one of my friends before the patch and I can make a team with him after the patch. But when I try to invite other friends they can't join our team. It's not working via steam invite. When I tried to search player they didn't show up (we are in the same guild) and when I click on "keep searching" and try to search them it says that this player is offline. We all updated game to the latest version. They tried to check files of the game via steam and it didn't work either. Reloading game/steam/PC/router didn't solve the problem. We all from Russia.