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

A bit heavy-handed, but it works.

1. Delete the user: Itunes Connect, Users and Roles, Edit, Select user, Delete
2. Re-create the user: (+), name, email, Next, Next, select 'Technical', Save
3. User will get a confirmation email, once they accept,
4. Itunes Connect, Users and Roles, Tap User's email in the list, Enable "Internal Testing"
5. My Apps, Select App, Prerelease, Internal Testers, Select the user, Invite.
6. User will get an email invitation, which they should accept from their device.

You're good to go.