Apple TestFlight : can't invite people

Question

I'm using the new Apple TestFlight for internal testing, I've invited a bunch of emails who all worked fine.

But I still have one who don't work.

So, I added the tester xxx@mac.com email in the internal testers section and configure it as an internal tester with Admin role. In the app prerelease section, I see that user, but with an xxx@me.com email.

And when I selected it and click on "invite" button, it says "invited", but the user didn't receive the email to test the app. And in the list, he's status is not like he is part of the test (not accepted and installed the testflight).

What's happening?

Answer 1

One problem that I found (and it's pretty crazy) is that if you enter the Internal Tester's name with any uppercase letters in the email address, you will not be able to complete the Invitation process for a specific app. I had this with two users and only deleting their User account and re-inviting them to iTunesConnect with the same email entered in all lower case solved the problem.

This was not an issue of them being both Internal and External Testers which is another known problem.