Have you found a solution to this? I see the same problem, this worked 6 months ago and now has changed. But they did not change the sample

https://developer.apple.com/documentation/appstoreconnectapi/app_store/in-app_purchase/managing_in-app_purchases

Found the problem. Should be "type": "inAppPurchases" instead of "type": "inAppPurchasesV2"