Group Folders not visible when trying synch to Windows 10

We have a NextCloud server working well, using Group Folders to control read and write access. Users can easily navigate the available Group Folders structure.

  • Server
    • NextCloud v18
    • Folders shared using Group Folders for read/write access
  • User
    • User has Windows 10 workstation with latest version of Nextcloud App
    • The App authenticates to NextCloud via a browser window

The App then presents the list of folder subtrees which it can synch from NC to the user’s workstation. But none of these subtrees are those which are made accessible via Group Folders - it only shows those which are shared via conventional “Sharing”.

Adding user to the Admin group fixes the problem, but that is not really a solution.

Any experience of using the Synch mechanism with Group Folders ? Some setting we are missing?