I had a similar TestFlight issue in July (builds processed fine but wouldn't install — affected my whole account). Feedback Assistant was useless, only automated replies. What fixed it: I opened a case directly with Apple Developer Support (developer.apple.com/contact). A senior advisor confirmed it was an account-level backend issue on Apple's side, they 'took action' on July 15, and told me to wait 48h and upload a NEW build — after that everything worked. Since your problem started exactly around July 15 and App Store Connect shows no errors, I'd bet it's related to backend changes Apple made then. Open a Developer Support case (not Feedback Assistant), mention it affects all your Mac Catalyst builds since July 15 while iOS works fine, and ask them to check your account/TestFlight config on their side. Also try uploading a fresh Catalyst build after contacting them — in my case old builds stayed broken, only new ones worked.

I am experiencing exactly the same issue. For the past several days, I have been unable to install or test any of my applications through TestFlight. This has completely blocked my development workflow. All builds upload successfully, are processed correctly in App Store Connect, and appear as available in TestFlight. However, every time I try to install a build, the installation fails. Here is what I have already verified: Builds upload and process successfully. The builds appear in TestFlight. Certificates and provisioning profiles appear to be valid. I have signed out and back into my Apple ID. I have tried different devices and users. The issue affects all of my TestFlight applications, not just one. I have already contacted Apple Support, but I have not yet received a resolution. At this point, I suspect there may be an issue with my Apple Developer account, TestFlight configuration, or a backend issue on Apple's side rather than with any specific application. Has anyone had their account checked or their issue resolved by Apple? If so, what was the solution?