Can't add user to TestFlight Internal group

Few days ago, I can't add my tester to Internal groups. Checked the api returning 500 as the attached image

Have you tried adding the tester through the Connect app?

Hi @dehrensdev I'm here, I've just tried but it show as this tried with 2 accounts of my organization but it's the same issue.

But I can add tester successfully with other organization

Can't add user to TestFlight Internal group
 
 
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