Same issue here. I tried it in Sandbox and in beta testing through testflight. Making a test purchase through the sandbox account in the app store settings also does not work. Here are the device logs (personal information has been censored) LiberaIAPLogs.txt

I solved the issue I had. Turns out I didn't set the StoreKit config in my scheme. Go to "Edit Scheme" -> "Run" and check if the config is set. If not, follow this guide: https://developer.apple.com/documentation/xcode/setting-up-storekit-testing-in-xcode/ It should look something like this if the scheme is set up correctly: