out of about 10 testers, only 1 was ever able to get internal testing to work. it was working for myself up until recently and it seems completely impossible to add myself to internal testing again.

I have been struggling with similar errors for days. My solution was eventually to take the development team id(in xcode copy the code that appears when you hover over the development team name) and put that into unreal-project settings- xcode projects-apple dev account team ID. all this time i was trying to input the name and didnt think to put in th e ID.