I am having this issue as well. My app was removed from sale, I uploaded a new build and am trying to test it using "TestFlight".
TestFlight shows the new build as "Testing". My test users get an email, re the new build, but when they try to install it the TestFlight app advises "Could not install . The requested app is not available or does not exist".
Obviously I need to test my new build before submitting it to the App Store.
