Zorin OS Lite won't power down laptop after shutdown

Hi all, please help, new Linux user here! I have installed Zorin OS Lite onto an old Acer Travelmate 2400 in an attempt to bring it back to life as it was an old XP machine. Everything has gone without a hitch, except for shutdown and restart.. of which it does neither!

After shutdown the OS goes to a black screen but to power-off the laptop I have to hold the power button down otherwise it remains running with nothing going on.

Can anyone tell me how I might be able to fix this? is it possible?

Suspend feature or Screensaver may be interferring with Shut down.
Can you disable all screen saver options from the Power Manager, set all automatic screen blanking to never and open a terminal and run: xset s 0 0.
Reboot (the hard way) once.
Then, test the shut down option from the menu?

Also, are you using Nvidia Graphics?