There’s an issue where some players are getting an “Unable To Create Match” message, we are very aware of this and are working on a fix.
With Game Center you can only have 30 active games at once, when you quit a game it’s possible for that game to remain active taking up one of those slots. We’re working on an update that will end games 100% of the time when it is your turn, however, this issue is still possible if you quit when it is not your turn. We are also working on a way to clean up as many of these stray games as possible. We are talking to Apple about this issue and are working with them to find a solution.
In the mean time I would suggest quitting as little as possible. If you want to quit on your turn it would be better to blow your tank up instead, and avoid quitting when it’s not your turn.