TestFlight Builds cannot be installed "not available/or does not exist"

When releasing a new version to TestFlight all testers receive invites, but nobody can install the app. I tried multiple approaches and released another 10 builds but it does not seem to be installable. (iOS 17 iPhone 12 and iPad Pro 3)

Did anyone experience something similar or know how to resolve this in a timely manner?

Thanks :)

TestFlight Builds cannot be installed "not available/or does not exist"
 
 
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