Sometimes the game and your account are not synced (e.g. this can happen when installing the game on a new device, or after updating the device itself among other things).

Please verify that you are logged into iTunes with the account you purchased the Upgrade with and try tapping the ‘Restore Purchases’ button inside the game.

If this does not resolve the issue for you, you may need to verify that your account is in fully working order. Apple requires an up-to-date payment method to be active, even when restoring purchases. If possible, trying the restore purchase process on another app is a fast way of testing the account. More information and options can be found here ( Apple Support).