@kubam2 have you had any luck with Support? Weirdly enough I'm having the exact same issue - brand new ATV 4K, registered via Xcode, and it showed up as "iPod" in the developer portal so I can't register it with a tvOS Development certificate

We've been experiencing the same issue since yesterday, the artifacts tab in Xcode shows the same 501 error, and App Store Connect shows artifacts could not be found. It's the same for builds done today/yesterday, and also for older ones which definitely had artifacts. I've raised a support ticket with Apple yesterday and I'll update here if I hear anything back