TestFlight builds show Complete but cannot be installed — "The requested app is not available or doesn't exist"

Since June 27, all new TestFlight builds for my app show Complete status but cannot be installed by any tester. Error is "The requested app is not available or doesn't exist." Adding testers to the build also fails with "There was an error processing your request." This affects all builds regardless of version number. Support case open for 5+ days with no resolution.

TestFlight builds show Complete but cannot be installed — "The requested app is not available or doesn't exist"
 
 
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