I have Ubuntu 18.04 installed with Gnome Desktop. My keyboard numerical keyboard is not working even after installing numlockx and checking that is showing ON from Dconf
Make sure to check that the numlock state is showing as 'on'
You can do this by pressing Ctrl+Alt+T and then running:
gsettings get org.gnome.settings-daemon.peripherals.keyboard numlock-state
There should be a return
If it is not, then run:
gsettings set org.gnome.settings-daemon.peripherals.keyboard numlock-state 'on'
Check again and confirm that it is showing as
Also make sure to log out and log back in or just do a full reboot to make sure that gnome has taken the new settings.