Paid with Apple, but app doesn't recognize payment

This problem can sometimes occur from payments through your Apple ID, when you pay directly in your app on your Apple unit. It's easily fixed however, so don't worry.

What you need to do is to log back on to your account and press Restore Purchase found in Profile > Create Subscription if the active subscription isn't automatically found.
If this wouldn't work, delete your app and re-do the process.