OK... in 15.3 lite LiveUSB, can you test this?
Set the settings in xfce power manager, then close the lid.
Login on LiveUSB is user: zorin pass:______(blank)
https://docs.xfce.org/xfce/xfce4-power-manager/preferences
Otherewise, these commands on Zorin OS Lite will work on XFCE desktop (Which is what I use):
Suspend Key:
xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/logind-handle-suspend-key -n -t bool -s true
Lid:
xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/logind-handle-lid-switch -n -t bool -s true
the above may require you to install power manager utilities. I am reasonably certain this comes included in Zorin OS Lite, but not 100% certain, so just in case:
sudo apt install pm-utils