Should you encounter any issues downloading a game, check the following:

• The storage space on your device (a game will not download if there is not sufficient space)
• Your connection (a bad connection can prevent a download from completing)
If you are still having trouble, please contact the corresponding app store.
• iTunes- https://expresslane.apple.com/Issues.action
• Google Play- http://support.google.com/googleplay/?hl=en