Here is a collection of the issues which our guys had:
for me:
I wasnt able to join a pw protected server. it said wrong password all the time. Ofc i restarted the game after every time. ( ~7-10 out of 24 men)
if the first problem didnt occured this one happend:
while in the loading screen to join the server it stopped and showed the main menu.
Update:
problems seems related to the newest .Net Framework which is released today. After installing the update it was possible for all people to join the server.