Whenever I play with my two friends online we always have issues starting a game because of this. The way we managed to start MM was using this method:
Someone else is part leader and they attempt to start but are greeted with the “One or more players is not ready” Message so then I say to promote me to party leader and then I start the game. The message doesn’t appear this time and the game starts searching. This goes on for a while and I eventually back out and then promote the other guy to party leader again, and weirdly enough, we are all back in the search menu and shortly after we find a match and the game begins.
WHY DOES THIS HAPPEN?!?!
This happens over half the time so I really can’t call it a rare issue. This happens anytime me and my two friends are playing online.