I am experiencing the same account-wide TestFlight installation issue.
All affected builds are successfully processed, valid, and shown as “Testing” in App Store Connect. Internal testers can see the apps in TestFlight, but installation fails with:
“Could not install [App Name]. The requested app is unavailable or does not exist.”
The issue affects multiple apps on my Developer Team, including Sykkylv1 and Bølge.
At the same time, App Store Connect/TestFlight incorrectly reports:
“Before you can use TestFlight to distribute beta builds of your app, you must renew your Apple Developer Program membership.”
My Apple Developer Program membership is active until March 19, 2027, and all relevant agreements are Active.
I have filed a Feedback Assistant report:
FB24450198
I have also opened an Apple Developer Support case.
I can provide the affected App IDs and any additional diagnostics if needed.