Try this:
;Artificial Inteligence Script
;Header
desc = Glow Stick
;Triggers
:state=0:globalvar=1,state=1
:state=1:mlightid=250,mlightrange=200,mlighttype=1,mlightred=0,mlightgreen=255,mlightblue=60,state=2
:state=2,scancodekeypressed=38,varequal=1:state=3
:state=3:mlightid=250,mlighton,mlightfollowplr
:state=3,scancodekeypressed=0:state=4
:state=4:mlightid=250,mlighton,mlightfollowplr
:state=4,scancodekeypressed=38:mlightid=250,mlightoff,state=2
;End Of Script
You need to use the 'mlightid' command before any other 'mlight' command so the exe knows which light you want to edit.
The 'mlightfollowplr' also needs to be called whenever you want the light to be at the same position as the player, each time it's called the light is moved to the player position.
Your script was moving the light when the key was pressed and then not after that.
knxrb