Why does "Gnome Software" (The GUI program) not show any updates?
It only checks for updates once a day so if you don't leave
your computer running all the time it doesn't find anything.
You can do:
on the command line
or change how often it checks:
Launch "Dconf Editor"
click to key "org.gnome.settings-daemon.plugins.updates"
Change value "frequency-get-updates" which is in seconds to something else.
The default is 86400 or a day.
You could change it to 3600 which is hourly.
I think there should be a button in Gnome Software to check for updates now.