I'm trying to implement receipt validation to check for the presence of an add-on, primarily by following the steps desribed in this article. In order to obtain a receipt for testing I'm closing the app with exit(173) but when I try to log in in the subsequent dialog with my Apple ID I recieve the error message "An unexpected error occured while signing in. The Apple ID you entered couldn't be found or your password was incorrect. Please try again." This happens not only for my Apple ID but also for another developer account associated with the app. Currently the app is set up in iTunes Connect as well as the IAP product, but so far have not been submitted for certification and shown as "Prepare for Submission".
It would be great to get some advice on how I have do proceed to obtain a receipt that I can use for further development and testing.