I got my app approved for distribution through the new Apple TestFlight app. I tried to invite an "internal tester" through iTunes Connect ->Prerelease ->Internal Testers
but all I see are 2 info boxes:
To start testing, select at least one Internal Tester.
Internal testers can be added in Users and Roles. Internal testers are iTunes Connect users with the Admin or Technical role.
I already added an Admin an Technical user to Users and Roles
but I can't invite them.
How to invite an internal tester?
it save me from going crazy)
Something else that might help is if you flick the "Internal Tester" switch on a user and it doesn't stay, you have to make sure, as Apple says in this doc "The user must have an Admin, Legal, or Technical role."
Problem solved: The email for an internal tester was also used for an external tester. As soon as I removed the email from the external testers list I could invite the user as an internal tester.
To add people to internal testers you need to go
To add a beta tester you must be signed in to iTunes Connect with an Admin or Legal account (NOT a Technical account). This answer explains further https://stackoverflow.com/a/27046745/3055537