Someone shared a folder with me on iCloud, I can see it on my iPad but not on my iMac, why?

Jan_BE wrote:

Someone shared a folder with me on iCloud by Adding Me and sending me the invitation via Messages. I received that invitation in my iPad and accepted it.

From that point on, I can see the shared folder on my iPad (and on my iPhone). The problem is that I do not see the folder on macOS (High Sierra). iCloud access is otherwise working fine on macOS: when I create files on my iPad they appear on macOS and vice versa. I just don't see the share folder.

Please advise.

macOS High Sierra does not support folder sharing. macOS Catalina or better is required.