How to sync my developer Apple ID in App Store Connect?

we have a developer added into our program, but his appleid is something like xxxx@inbox.appleid.apple.com

when we try to add him into our testflight inner tester group, we failed due to "invalid email address",

now he has change his apple id into a normal email, how to sync it to the apple id in applestoreconnect ?

[Edited by Moderator]