It works now. Now I can use my Sandbox account for my in-app purchases. I didn´t know that I need to sign out on my iPad Air under: Settings-->select my Apple Account-->Select Media & Purchases-->On the pop-up menu, select Sign Out. https://developer.apple.com/documentation/storekit/testing-in-app-purchases-with-sandbox

I had already symbolicate the crash report. See my previous reply. What does (:1) mean? In which line in my class did the error happened? Is it normal that there is no error or exception message displayed here?

I have downloaded the crash report from TestFlight. Then I have modified the app name and developer name in the file crashlog.crash and changed it to crashlog.txt. You can download the crashlog.txt file here: https://easyupload.io/r5ahaw Do you need the feedback.json file?

I know that a player gets an e-mail with the receipt and ORDER ID when he makes an in-app purchase in a published application. Where could I find this ORDER ID in my App Store Connect account when my application would be published and when the player would purchase an in-app product in my application?

I know that a player gets an e-mail with the receipt and ORDER ID when he makes an in-app purchase in a published application. Where could I find this ORDER ID in my App Store Connect account when my application would be published and when the player would purchase an in-app product in my application?