Requesting an In App Purchase in iOS 13 fails

Restarting Xcode and simulator did the trick: now my in-app purchases load properly in iOS 13 simulator.

EDIT: This happens in release Xcode 11 too. And happens once in a while, but restarting Xcode and simulators still helps.

EDIT 2: In Xcode 12 beta this bug is also present. But the solution is to create new StoreKit Configuration file (in File -> New menu)

Then add all your products there. Use the same product id's as in AppStore Connect.

Then add this file to Run Scheme configuration.

Note: I've updated the answer, read the Edit part.

To share my experience, it seems that this problem does not exist any more in Xcode 11.1 GM Seed. There's no need to restart Simulators or Xcode to make in-app purchases work anymore.

I had submitted an app for review and it was rejected because of that particular error. As it turns out, it was rejected for a stupid reason as it wasn't my app's bug, however I spent hours trying to get around it.

So, just update to Xcode 11.1 GM Seed and run again. Everything will be okay.

EDIT

The issue still exists in Xcode 11.1 and apparently I was just lucky that it didn't happen to me again. However, I had a second rejection for the exact same reason. What eventually worked and made my app get approved was this:

I had to update my IAP record on App Store by editing and saving it again.

So, I recommend you to try the same; change something temporarily in your IAPs, save and then revert your changes (and save again) so records on the App Store to be refreshed.

FYI, after the second rejection Apple invalidated my IAP and therefore showed me the way. It looks like to be a known issue to them at the end.

For details read this discussion I wrote on Reddit.

I had the same issue, iOS13 Simulators produced the same error, iOS12 Simulators were working well. I then tried out on the iPhone with iOS13 installed, there the calls were working flawlessly too.

Hoping that it'll be fixed soon in Xcode Simulators, I guess until then we are stuck with the error.

Edit: Now it seems to work also in iOS 13 Simulator Devices.