iCloud Drive missing from Finder Favorites List

When I bring up a Finder window, I have always seen iCloud Drive in my list of favorites. Recently it disappeared.

However, the iCloud Drive is still there - I can search for a file in the Finder Window and when it is found, I can choose "Show in Enclosing Folder". But since the iCloud Drive seems to be on the root level when I right-click in the title bar of the window (which shows levels of nesting), I can find no other way to access it.

Does anyone know how I can get iCloud Drive to reappear in my list of Favorites?

Thanks.