I just made a mac catalyst app and the Bundle Id shown in Xcode is "maccatalyst.com.***.***".
However I cannot register a Bundle Id in the App Store Connect with the same name.
I tried several times and find the problem might be Bundle Id cannot be start with "maccatalyst".
In this situation, I cannot upload the app build to App Store Connect because the Bundle Id is mismatched.
Is there any way to solve it?
Found the solution by my self.
Go to the Certificates, Identifiers & Profiles page, click your identifier of your iOS app. Check "Mac" from the Capabilities. The Bundle Id is then created on the App Store Connect side.
Once you click on the Mac capabilities, do you need to re-upload the iOS app or anything special?
In case this helps anyone else, note that the format is of the form "group.DEVELOPER ID.maccatalyst.APP ID"
If your developer ID is ABCDEFG then you typically need to add the app group "group.ABCDEFG.maccatalyst.com.yourcompanyname.yourappname" on the certificates website.
This took me DAYS to work out, due to a not-particularly helpful error message.
Also you need to be using modern URL-based methods to load and save files, the one my iOS app used was deprecated.