There is currently a bug that prevents players that are muted in a Blizzard game to play Diablo III… it won’t let you join a game nor start a new one until your silence ends.
The Customer Service folks have already said that this forum is the wrong place to post on this issue; see Start Game Greyed Out - Unable to join game, only available to party leader - #455 by Drakuloth. There is a bug report, and that is where you should be posting or following to find out any news on this issue; see: Silenced players not able to play
You can appeal your ban/suspension/mute here:
https://us.battle.net/support/en/help/product/services/316/980/solution
Click on the Contact Us button at the bottom.