Same issue on my account since September 19, 2026, still not resolved. All TestFlight builds across all 4 apps in my account fail to install with "The requested app is not available or doesn't exist", including a new build uploaded today (Kaldero 1.0.1 (81), Apple ID 6762309229), which shows as valid and in testing in App Store Connect. Already tried: new builds with incremented numbers, reinstalling TestFlight, restarting the device. Account, agreements and membership are all in good standing. Feedback: FB24851259 Developer Support case: 102968877610 (opened September 19, no answer yet)