Try to check the receipt validation in sandbox environment rather than storkit.

• Create the sandbox tester account on the Apple account

• Add that sandbox account on your IOS device :: settings -> App store -> Add sanbox tester account

• disable the storekit configuration on the xcode , go to product - > scheme -> Edit scheme -> Run(on left side) -> in Option Tab set storkitConfiguration to "None"

(Make sure for in-App purchases your App should have signed App agreement, then only you can fetch products in sanbox and Production environment)

Docs for your reference

Paid Agreement for in-App purchases https://developer.apple.com/help/app-store-connect/manage-agreements/sign-and-update-agreements/

sandbox Testing

https://developer.apple.com/documentation/storekit/testing-in-app-purchases-with-sandbox