Can't Join Friends In Game

Got an invite from a friend to play. Hit accept, and now I'm sitting in the main menu with the message "Waiting for leader" (if i hit PLAY) but otherwise I just SIT here, while they're all still in a game. (it's checkpoint, so I really see no reason why I can't join)

Had to wait for their damn game to finish... ugh

that means the ivites are not working for game yet.
and as you may know, you will have to wait till the party leader joins a new match.