Laptop screen is blank or off (all dark and nothing, like off)

i was in “energy saving” to enable the laptop lid close action to sleep…
and i was typing msg to thanks the guy in the forum to teaching me where to make lid close sleep work… i think i pressed some button wrongly… or maybe that has nothing to do with it… after i posted the msg, i realized my laptop screen is blank and black or off… only the 2 monitor is still on and working…

what made my laptop screen go blank ?
i know in windows, there is button to set “extended display, duplicate display, projector screen only (laptop lid blank)” … but here in linux i have no idea. the original hardware button for that purpose does not work in linux (i wonder if anyway to make it work like it suppose to).

need assistance.