You can try the following workaround:
1. Delete the app.
2. Restart the device (hold down the sleep button and then tap Power Off).
3. Reinstall the app.
4. Go to the in-app Settings and tap the Restore Purchases button.
2. Restart the device (hold down the sleep button and then tap Power Off).
3. Reinstall the app.
4. Go to the in-app Settings and tap the Restore Purchases button.