Currently you specify max players, but this still allows the game to start without the desired number of players. Some players (who didn't open the game) try and control the start of the game by not setting "ready" until the desired number of players join, which just seems counter productive.
Please change max players to player. Then everyone can go on ready knowing that the game won't start without exactly 4 players. Then if the room owner wants to change to a 3 player game, it resets everyone back to "not ready" (so that there is agreement on changing to a 3 player game).