Question motherboard vga not working, plug in discreet video card and still not working

[limkuncui]

I have a motherboard that only have 1 VGA video out, and no other display out.
Unfortunately the vga output from motherboard is not working and the lcd display show no signal message.
(I confirmed it by plug in the vga cable to my laptop and it can display just find that means my motherboard vga out is not working)

So I try plug in a discreet video card to that motherboard, but when I connect the vga cable to the discreet video card, there is still no signal.
Is there a settings that I should enable at the bios? with my primary motherboards vga out is not working, how can I enable it?

I'm using asus motherboard.
can anyone help me with this?

best regards

 

[rgd1101]

full system spec? include brand and model of the psu

 

[limkuncui]

It's an old PC. I can no longer look at the PC specs
I think it's intel i3 Gen3 if I'm not mistaken. Using asus Motherboard.