There's a bug that stops any new games from starting on mp servers. The timer runs down, but then stops. The only way to get the room playing again is if everyone in the room joins the spectators at the same time. If the next game starts instantly after the last, the glitch continues.

It might be caused by a player disconnecting (no response) just as they lose, as I noticed that happened the last time I saw the glitch (seen it 3 or 4 times now since 4.5 or so)