Hi, drag and drop from server to client is not available when the display server is Wayland. You can read more about this here:
https://kb.nomachine.com/AR02P00969. See point 2) in Known limitations.
Gnome removed the drawer showing 3rd party application icons a while back and as a consequence, it’s no longer possible to display the !M icon in the system tray out-of-the-box. You should install a special extension which is described in the following article:
What to do when the !M icon is not present in the system tray of GNOME desktop
https://kb.nomachine.com/AR09U01205