Did you try to close the app in the multitasking dock (press twice the home button, tap and hold the app until it twiggles and tap the red dot)?
If yes, did you try to restart the iPad (switch off/ switch on)?
If yes, did you reboot your device (long holding power and home button until the Apple appears afetr shutting down)?
If yes, did you try to delete thenapp and re-install it from the purchased items?