When working on the Xcode 15 bindings for PassKit, I noticed the PKPayLaterValidateAmount function has a completionhandler that always returns false no matter what value is passed into the function. I also tried to set up a physical device with a Apple Pay Later card approved and set up and the test results did not change. There is no documentation about what should cause this function to return true, but I created an issue with Apple that can be found here: https://feedbackassistant.apple.com/feedback/13268898.
Until we figure out if there is a bug here or more initialization is needed, I will comment out the code enabling the PKPayLaterValidateAmount function.