Sound like there is an issue confirming the purchase with App Store server for some reason. Here are a few things to try:
1. Apple’s recommended first step is to restart your device and then try restore purchase again.
2. If that doesn’t work, then please choose “Free Trial” option, wait a day and then try “Restore Purchase” again. The App Store issue should fix itself with a little time.
If the above still doesn’t work, then please let me know and we can dig deeper to see why? Please also attach the screenshots of the purchase record and settings page with the status. This will help to troubleshoot the case, contact us via email [email protected]