If that's the case the issue isn't related to IAPHUB but most likely because iTunes isn't returning the products.

You should double check you're able to load the products for sale in sandbox. You should first find out if the reviewer couldn't fetch the products for sale or had an error during the purchase. If you receive this message it is simply not the reason of your issue, IAPHUB is validating the receipt using the recommended approach. If validation fails with the error code 'Sandbox receipt used in production,' you should validate against the test environment instead. The recommended approach is for your production server to always validate receipts against the production App Store first. 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 reviewer will sometime provide the 'Next steps' to resolve the issue, it is usually not very helpful, the most common message is the one below You might receive a rejection because the reviewer reported an issue even if everything is working fine on your side in sandbox, disturbing right? Let's try to find the cause of the rejection. You've implemented IAPHUB in your app successfully, everything is working great in sandbox and you're ready to release your app on the App Store? The Apple Review team will test your in-app purchases implementation before approving your app.

Receipt validation apple sandbox