Building iOS App with iCloud enabled fails

Pretty much as the title describes.
When I add the iCloud option to my App, and tick all the boxes, I get this failure message at the signing stage:

I looked at the older similar topics and it indicated that this had been fixed. Any thoughts on what I’m doing wrong here?

OK - I think I have found the problem - I need to use “Edit your App ID Configuration” in the Apple Developer site to add the iCloud Capability.

Do I need to edit the configuration on the Apple site by adding an “iCloud Container” there, or is this done by Xojo during compile using the default option?
Or do I need to add an identical one on the site and in Xojo?

Xojo doesn’t create containers for you, but it does alter the plist an entitlement files when it builds to support these things.

So does that mean I create the containers on the Apple developer site and matching ones in the Xojo iCloud options?