We are in the process of trying to get approved in the App Store submission process, but have faced a rejection due to a payment failure when the reviewer attempted to subscribe. While testing the payment process, we have encountered the following errors: 

“The receipt is not valid. The purchased product was missing in the receipt. This is typically due to a bug in StoreKit.” 

and 

“There was a problem with the App Store.”

Are these issues associated with the Apple Sandbox environment when testing payment? From a bit of research, this seems to be the case. If so, how can we be approved by Apple if the only way to demonstrate the functionality of payments is by testing in Sandbox mode? In the review process, we received the following information: 

When validating receipts on your server, your server needs to be able to handle a production-signed app getting its receipts from Apple’s test environment. The recommended approach is for your production server to always validate receipts against the production App Store first. If validation fails with the error code "Sandbox receipt used in production," you should validate against the test environment instead.

How can we achieve this setup with Revenuecat?

 If what I’ve provided thus far is insufficient, what further information is needed to diagnose the problem?

 Thank you for your help.