Can't add Internal test user

I'm an owner of app and have Admin role. I'm trying to add internal tester and getting:


You can't add any additional internal testers.

Manage your Internal Testers in Users and Roles.


For now i have one internal tester(me).

What should i do to add more internal testers?

Same issue here. Maybe too late to ask, did you figure out?

Can't add Internal test user
 
 
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