No TestFlight invite email gets sent for internal users

Question

I set up my application for TestFlight. For external users it is waiting for review. But if I want to invite internal users, I select them and press invite. iTunes Connects says

Answer 1

My solution: Use an App Store Distribution profile, not an Ad Hoc Distribution Profile for submitting your app.

And secondly, you have to recreate the App Store Distribution Profile before submitting the app. This will add the betatest entitlement to the profile.

Maybe you need to remove the internal testers from the list and add them again.