Unfortunately, it seems the launch of the new maps was botched -- we've received a number of tips claiming the maps aren't loading in-game. Major Nelson recently Tweeted that the game needs a title update in order to incorporate the new content, which he says is coming soon. We'll let you know when everything's in working order.
Update: The Major just confirmed that the title update is live, and should be available worldwide in "a few minutes."
[Thanks to everyone who sent this in!]