This is a confirmed bug, which seems to have been there since the beta2
version of 16.04, as some users reported in Ubuntu Forums. Its importance has been set to critical, so it'll probably be solved soon.
People have reported two different ways to solve this:
- Temporary fix: log out and log in
Permanent fix: fire up a terminal and run the following:
$ mkdir -p .config/autostart $ gedit .config/autostart/menus.desktop
And add to the file this content:
[Desktop Entry] Type=Application Exec=initctl restart unity-panel-service Hidden=false NoDisplay=false X-GNOME-Autostart-enabled=true Name=menus Comment=Show me the menus X-GNOME-Autostart-Delay=
X-GNOME-Autostart-Delay=
value is empty on purpose, but if the fix doesn't work properly, you might need to add a 1 or a 2.
Source