same problem here (on iOS app, it did not gave problems on Maccatalyst apps) I just contacted appstoreconnect.com, they wasn't aware of this problem and do not provide a solution for it try to contact them too I found also a post on stack overflow, with a possible solution, but it didn't worked for me: https://stackoverflow.com/questions/62442805/ios-app-submit-review-to-app-store-failed/62462336#62462336

Today I tried again the Appstore connect error message was improved: the error show was still there, but additional informations were available my "new in this release" notes wasn't there anymore and it was necessary to add them manually again for each language finally I arrived to release my apps what did caused my release notes disappear? I discovered this is an error with the Fastlane tool I'm using for deploys of binaries and metadata, it seems that with metadata it is not working anymore (since the App Store connect redesign) and my notes for the latest version wasn't there with the correct error message I solved the problem