I've developed an app that is available for testing on Testflight now. I've created a link for external testers with no criteria. Over the last week I've had several people contact me and tell me that they are not able to install because they are being asked for a 'redeem code': "Enter your TestFlight invitation code." The problem is, the user shouldn't be seeing this. They should tap the invitation, download/register for Testflight, then tap the link for my app to download install the app. However, that only happens sporadically and other times users are prompted for this redeem code. And I have been looking for solutions to this for hours and all I see are hundreds of posts dating back 5 years or more, but cannot find any solution anywhere. Cannot find any simple instructions to send to users or a link, and I cannot find any indication that Apple is even addressing this problem. Please give this post a boost so that someone at apple finally will address the problem.