i submitted app to apple but they reject and sent this message how i can solve this please help me Guideline 2.1 - Performance - App Completeness We found that your in-app purchase products exhibited one or more bugs when reviewed on iPad running iOS 12 on Wi-Fi. Specifically, an error message occurs when we attempted to make in-app purchase. Next Steps 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.