Tester invite getting kicked back saying invalid

Here is a screenshot of the error they are telling me they see every time.

I have the same issue. Name and email are correctly filled with no special characters.

I have the same issue. I can't add anymore testers to our internal test group. If I remove an existing user from the group, I can add that user back, but no new users are allowed.

I am getting the same thing. I have two custom domains configured on iCloud. For one I get the same msg as above "1 tester has an invalid name or email address and wasn’t added." with the other it accepts the email, invited received. The first one that fails, is my Apple ID though so I would like to use that.

I have the same issue. I tried to remove the tester (myself) of all our apps (30+), and tried to add it again. With some apps it is possible to add the Apple ID tester, with some apps it is not.

Why is there no real support for testflight? How do we get these issues resolved???

I submitted a bug report through the Feedback Assistant app. This is the first response they gave:

Thanks for your report. We need additional information on this TestFlight issue.  

First, please try the following troubleshooting:

1. Remove the affected testers from all Internal and/or External tester groups
2. Remove the affected testers from the All Testers tab under General Information 
3. Reinvite the testers to the correct group(s)

If the issue persists, please provide the App ID of the app you are trying to add testers to.

Thank you.

I tried the above steps but it didn't help. This happens with all of our apps.

I can also reproduce this issue. Reported to Apple: FB9994703

I got the following response from Apple for my feedback report. Following these steps did work for me:

Engineering has provided the following information regarding this issue:

This error occurred because a different Apple ID accepted the tester invitation for ***@.com, and a tester can be linked to only one Apple ID.

To unlink the two Apple IDs, take the following steps in App Store Connect:

1. Remove the impacted tester from the All Testers tab in TestFlight for all apps.

Note: Testers in the Deleted state aren't fully removed from TestFlight until their last installed build expires.

1. Re-invite the tester.
2. Make sure that the tester is logged in to the TestFlight app with the correct Apple ID when they accept the new invitation.

For details about how to manage testers in TestFlight, go to App Store Connect Help.

https://help.apple.com/app-store-connect/#/devfd291ca86

Any news about this issue?

Unfortunately the suggested workaround does not work.

Yes, I'm still having issues as well. Also, a previous account that I deleted from Users and from the testing list reappears every time I come back in.

Same problem. The suggested workaround doesn't work. Anyone else experiencing this?

Same problem here. It's been going on for a few months.

Also experiencing this issue!

I'm also facing the same issue so I've sent Apple my feedback on Feedback Assistant as FB10748429.

The more feedback, The more they care about this issue.

Unfortunately, Just posting "same" or "any news?" in the developer forums never changes Apple's priority. The only way to change it is to submit feedback on Feedback Assistant.

As far as I can see, only dcordero sent feedback on this thread but it's not enough.

I need your help. Please submit your own feedback and let's change Apple's mind.