I created a Sandbox account in order to test in app purchase in my application. In development mode I have no issue but during TestFlight it becomes tricky. Since I can't log in TestFlight with a Sandbox account (https://stackoverflow.com/questions/38034491/unable-to-log-in-with-sandbox-test-users-on-device) I need to be logged with my personal account to log in TestFlight and download the application. Then, I need to logout from my personal account, open my TestFlight app, try to subscribe to in app purchase, log in with my Sandbox account when Apple popup showing up. Then, after testing is done, I need to log in TestFlight with my personal account in order to get the next TestFlight version of App. I can't believe this is the "real" process and there is not a better solution to access TestFlight new app version while testing with Sandbox account. Also, if you ask me "Why I'm not using my personal account to test in app purchase in TestFlight?", it's because I have done it during years now, and my account is ****** up when I'm testing. My account retrieve thousand of transactions, "unfinishable", resulting in failure in TestFlight when everything works in production. My coworkers experienced the same issue with these "unfinishable" transactions and we can't use our personal account to test in TestFlight.