Same issue. Make sure you use the KEY ID (something like 78N8S6XAVY) and not the key name that you gave it. See key details by clicking the keyname.

I'm afraid it doesn't work. I only checked that the app could validate. And it validated fine - which it didn't before. But when I got to actually reviewing the app, I got: Unable to Add for Review The items below are required to start the review process: New apps and app updates must be built with the public (GM) versions of Xcode 11 or later, iOS, macOS, watchOS, and tvOS SDKs. Apps built with beta versions aren’t allowed. This build is using a beta version of Xcode and can’t be submitted. Make sure you’re using the latest version of Xcode or the latest seed release found on the releases tab in News and Updates

This problem is that $CI_WORKSPACE no longer works, change it to: $CI_PRIMARY_REPOSITORY_PATH