I'm running an Archlinux system with i3 as a window manager and nm-applet does not display an icon or respond to mouse clicks. It used to in the past, and does on some other systems with (as near as I can tell) an identical setup.
- If nm-applet is run with sudo, it does display an icon and does respond to mouse clicks.
- If you click on where the icon would normally appear and wait for a minute or two, the list of wifi networks will appear and function as per normal until nm-applet is restarted.
When running nm-applet from a terminal as a normal user it displays (after a minute or so):
(nm-applet:1701): libnotify-WARNING **: 04:16:33.115: Failed to connect to proxy (nm-applet:1701): nm-applet-WARNING **: 04:16:58.141: Failed to show notification: Error calling StartServiceByName for org.freedesktop.Notifications: Timeout was reached (nm-applet:1701): libnm-CRITICAL **: 04:16:58.142: ((libnm-core/nm-setting-connection.c:220)): assertion '<dropped>' failed