Do you have a problem with purchasing the Pro version? Do you get an error message when you try to make an in-app purchase?
This can be related to a temporary error on the App Store. Please check the below.
1. Log out from App Store and re-login
In-app purchase is available only when your current App Store ID is the same as the one you used to install the app. If you are using multiple App Store IDs, please make sure if you are using the App Store with the same ID. Or delete the app and reinstall it.
2. Check your network state and try again
This can be related to network failure. Please try again with the Wi-Fi network.
3. Try again after a few hours
App Store might be having errors, and mostly they are temporary. Please try again after a few hours.