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

only users with permissions can be added as Testers

steps to follow.

1. https://appstoreconnect.apple.com/WebObjects/iTunesConnect.woa/ra/ng/users_roles

2. https://appstoreconnect.apple.com/apps/1494800176/testflight/users

   Internal Group
           App Store Connect Users