I had the same problem. I called support, but ended up talking to someone in sales. They told me to go to the App Store app and click on purchases. Sure enough, the download got hung up. So, I just clicked on resume and it worked.
Has anyone else had trouble viewing movies with DVD Player on Airplay mirroring? When trying to watch movies using DVD player, all I get is a gray checkerboard pattern on my computer monitor as well as my TV.