So... this is probably not going to be very clear... I've been playing a bit of coop but I've had some issues. I can join people's games, people can join mine as well and the same goes for the person I want to play with but when we try and play together it weirdly doesn't work.
The only difference I can see between us two and the others would be that our accounts are both linked with the steam family sharing beta thing but I don't really think that has anything to do with it. Any ideas?