Please make sure you’ve download the free LetterSchool app on your iPad as well; you can use this link: https://itunes.apple.com/us/app/letterschool-lite/id481067676
You can restore your purchase via the menu in the app. Please go to the menu in the app – and scroll a bit down. There is the button ‘restore’. If you click that button, the full version will load correctly .
Important: You should be logged in with the same Apple account you’ve used for purchasing the full version. That way Apple automatically verifies the purchase.