The pro version is bound to your Google Account so as long as that remains configured as the first account in your device settings, it should stay active.
In some rare occasions, the Google Play license verification may get bugged. In this case, you can force a new license check by clicking the cart button in the main list followed by the refresh button. If the license check is successful, the product you paid for will be marked as "Active". Otherwise, please follow the steps below.
- Reboot the device and force another license check.
- If you use more than one Google account, make sure that the purchase account is on the first position in you list of accounts. If changes are necessary, perform 1) afterwards
- Open the app manager (e.g. "Apps", " Manage Apps", ...) in your device settings. Find the Google Play Store and press the "Clear data" button and "Uninstall updates". Afterwards, open the Play Store - you should be asked to accept the terms and conditions again and it will probably be updated again soon. Lastly, perform 1)
- Uninstall Deliveries completely. After reinstalling, the license will be checked upon first opening it again.