The System Status page says that the notary service is up, but every time I try it, I get "Failed retrieving request UUID for upload". I tried with 2 apps, and both Xcode 12.5 and 13.0 beta 2.
Developer ID Notary Service down?
When I log in to App Store Connect, I see a notice about "Review the updated Paid Applications Schedule." I wouldn't have thought that something about paid applications should affect notarization, but I bet this is the problem.
Once the account owner agreed to the Paid Applications Schedule, notarization worked again. Notarization could certainly be made more user-friendly.