Indeed, as @RayWha mentioned, this issues has been sorted - it looks like the API is not returning a 500 anymore and I was able to access XCode Cloud successfully from both AppStore Connect and the XCode app.

Something else that I did find out is that it looks like this is an issue at the account level and not at the app level as I am getting the same error when I go to "AppStore Connect > Users and Access > Xcode Cloud". The loading spinner doesn't stop as the requests to the same endpoint as failing with a 500 error.

The issue is still there for me—I’ve tried so many different things but haven’t had any luck yet. The API keeps returning a 500 error.

I do have the same issue. I was using XCode Cloud for my app with no issues until this week, when I transferred my app to a new "empty" company developer account. I'm trying to enable XCode Cloud again but I do get a spinner on AppStore Connect > Apps > My App > Xcode Cloud. When inspecting the requests of the website, I can see an API failing with a 500 error so I assume it's just an API failing for some reason and Apple are aware about it. 500 Internal Server Error https://appstoreconnect.apple.com/ci/api/teams/123123-123123-123123-123123 On the XCode app, the "Create Workflow" option is disabled so I assume it's related to above issue with the API? I pinged support two days ago but haven't heard back from them yet - will let you know if I figure things out.