iOS, Android, and Windows 8: Try uninstalling and reinstalling the app. Any titles you have purchased will be saved.
Should this fail to solve your problem, please contact our Customer Care Team at firstname.lastname@example.org and mention:
1) your user ID and password (so that we do not have to reset it);
2) the version of iPad you are using, 1, 2, 3 or 4;
3) your iOS version;
4) the problem you encountered, the situation you encountered it in, and a screen shot of any error messages.
For any other problem, please contact our Customer Care Team at email@example.com.