Unity 2020.1b3
Well I just been rejected by apple :
Then also sent a screenshot which I cropped :
App is working fine on android, and app already on the GooglePlay store.
We also do not have any problem using user test from the iOS build on devices.
Able to get the product detail from apple server, buy the non-consuming product, kill app, reinstall and restore purchase as well…
Really no idea why apple is having this message… any idea? 
… it’s actually a first…
Thank you! 
It seems I’m having a similar/same problem. I got rejected recently by apple twice with: Guideline 2.1- In-App Purchase would not complete. Everything seems to be working fine on test flight but for some reason, it is not during the review. Checking my analytics data it seems the purchase failed with the reason: Unknown. So not much help there.
“Submit this JSON object as the payload of an HTTP POST request. Use the test environment URL https://sandbox.itunes.apple.com/verifyReceipt when testing your app in the sandbox and while your application is in review. Use the production URL https://buy.itunes.apple.com/verifyReceipt when your app is live in the App Store. For more information on these endpoints”
Validating receipts with the App Store | Apple Developer Documentation
Are you validating your IAP receipts? Unity - Manual: Receipt validation
Actually… I do not… had no idea. …
I will dig into it right mow then, thank you!
So far I am doing it in the very basic way I believe…
Been using Prime31 plugin years ago, then back on rail with Unity services 
If by chance you could maybe double check those 3 pictures below if I didn’t make it wrong…
Thank you!
Unfortunately you can’t easily do receipt validation with Codeless IAP. When we first developed and released Codeless IAP, Apple did not require receipt validation. You could directly edit IAPButton.cs but is not supported, and your changes could be overwritten when you upgrade IAP if you’re not careful. You would be advised to use IAP scripting instead, as used in this IAP Sample Project https://discussions.unity.com/t/700293
Thanks!
I made the integration from your code sample, seems to work a charm.
Now on the receipt validation from the documentation :
So far Unity doesn’t like those :
Application.identifier
?? no idea
From Google https://discussions.unity.com/t/738559
@JeffDUnity3D Yup thanks!!
It seems it passed the validation center.
But I am back to a first problem I had a while ago :
Really that sucks. 
Sorry, I’m not sure what validation center you are referring to. Did you submit again? I replied on the forum thread you linked to. Did you edit the DeviceSettings.mm file?
Ah yes sorry, I was talking about Apple support.
I also juste replied to that message as well
So a little update from me, maybe it will help people having the same issue in the future. Yes, I’m using local receipt validation. I was rejected for in-apps not working twice after with I asked reviewer on resolution center to provide me with some logs because the app works fine on testfight. Instead of a reply, two days later my game changed status from rejected to in a review and 6 days later was approved for the App Store. Because of this, I can safely conclude that it was a problem with Apple’s configuration of the testing environment. Because I was rejected twice I assumed it was a problem on my side and wasted a lot of time searching for a fix. I found some threads with people reporting they had the same/similar issue. Unfortunately, they never provided updates if it was resolved and if yes how. So here is my update.
THANK YOU for taking the time to write this. I went through the exact same thing and your experience saved me a lot of time and anxiety.
