It has come to my attention that some players are having connectivity issues, especially when joining via friends list.
I'm currently working on an update for this. In the next patch there will be an engine update and API update to steams network. I'm counting on these issues getting resolved with this update.
If you get disconnected the first time you try and join friends list, close the game and restart and try and join again. If that doesn't work, you can create a server with friends only and join via the server browser.
In other news, I'm happy announce that a third multiplayer maps is being worked on and will be released with the connectivity issue patch.
Sorry for the inconvenience and thank you for your patience.
Cheers
Icehelm