App purchase has no receipt

I need some help in getting a receipt for an app I just purchased for audio converting on the App Store.

I bought x2pro for $249.99 and then was not emailed a receipt. I followed instructions for retrieving a receipt by going to https://reportaproblem.apple.com/?s=6 but the app just has "This purchase doesn't have a receipt" next to it. Not sure why as I paid money for it so it should have a receipt.

Any help much appreciated.