Sometimes the messages from Apple's IAP server are not received correctly by our app (e.g. payment processing delays) causing this to happen.
To resolve this go to the Pro Purchase screen again and use the "Restore" button. This will ask Apple once again if you have purchased the app and then unlock the app for you.
At times you can be asked to purchase again when you do a restore, don't worry if that happens. Just go through the purchasing flow again (tap to buy, confirm, and put in your App Store password) and you'll get a pop-up notifying you that you've already paid for it. Please note that you must use the same Apple ID that you initially used to buy the in-app purchases. If you use a different Apple ID, you will be charged again!
So make sure you are using the correct Apple ID
If you need further assistance then please contact support.