Please use the Restore option for the games purchased from inside the app:
- Run the App Store app on your device
- Make sure your are signed in under the same Apple ID that you used to buy the game
- Go to the Purchased tab and tap the Cloud button next to game
- Run the game and tap the Buy Now button in the main menu of the game
In the new window, tap the Already Paid button and enter your Apple ID and password. Make sure you sign in under the same Apple ID you purchased the game. The game will be unlocked.