The in-app payment window is not displayed on the commercial apps deployed in the App Store. (IAP is subscription type) It is a WKWebView app, and in the development environment (build, testflight), the in-app payment window is displayed when the product button is pressed (sand box environment) This app has been commercially distributed. And when you press the product button in actual commercial, the in-app payment window is not displayed. Before payment, access the apple receipt server corresponding to the commercial server, determine whether it is [already subscribed] and display the payment window. [Example] https://buy.itunes.apple.com/verifyReceipt I got you to call. The source code related to No. 3 above is complicated, but there are many do-catch and if-else, and if it does not work normally, the source code is written to display an error message using an alert, but the alert is not displayed in actual commercial use.