FB15564997 - If someone could please take another look at this that would be awesome. To Reproduce the issue: Invite an internal tester to join TestFlight (i.e. appleid@<work.com>) Accept the internal invitation from a device signed in with an external Apple ID (i.e. appleid@<personal.com>) You now have access to internal builds from your external Apple ID Attempt to accept the invite from a device signed in with the internal Apple ID (i.e. appleid@<work.com>) You can no longer redeem the code from your internal apple id. Doing so results in an error from TestFlight stating the code is invalid and cannot be redeemed. Suggested Troubleshooting Steps Provided by Apple: To unlink the two Apple Accounts, take the following steps in App Store Connect: Remove the affected tester on the “All Testers” pane in TestFlight for all apps. Note: Testers in the “Deleted” state aren't fully removed from TestFlight until their last installed build expires. Testers have access to installed builds for up to 90 days, even if you manually expire the build in App Store Connect. Invite the tester again. Make sure that the tester is signed in to the TestFlight app with the correct Apple Account when they accept the new invitation. Issue Continuation After clearing the internal tester from "All Testers" pane in App Store Connect and adding them back as an internal tester. They received another invitation with the same invite code as from step 1 earlier. This results in the same error message which appeared in step 3 earlier. Couldn't redeem TestFlight invitation code. This invitation has been revoked or is invalid. Request a new invitation from the developer. Bug Identification Because the invite code is not switching out during deleting / re-inviting the user, the code can never be redeemed by any user outside of the external Apple ID that wasn't the intended target to begin with. Quite possibly the simplest high-level logic implemented Apple side would be to make any “invite action” generate a new code (and expire any old code / remove Apple ID from testing) so that users have a way to fix the issue whereby codes become locked to a certain Apple ID.

User can redeem the code on devices that are signed in with the personal apple id.