BIOS suddenly not detecting GPU

[midiout]

I turned on my computer today and my monitors did not display an image. I could hear windows boot up as well as skype alerts, but no image on either screen. I though at first my video card ate it, but apparently that's not the problem.

I tested my video card (gtx 780) in my old computer, and it's working just fine. So I then assumed my motherboard was to blame, which was an instant headache. So I took an old video card I had in my closet (gtx 560), put it in my 'new' computer and it's working as expected.

So my 780 works in my old computer but not my current one (even though it has been fine for a few months), yet my 560 works in my current computer.

System Specs:
http://ca.pcpartpicker.com/user/brooker/saved/jj6323

BIOS hate:
https://imgur.com/ljV7gaq

I've done some reading around and I can't find anyone with this specific problem. I've made sure the card is seated well. I've changed the power supply cord. I've moved it to the other PCI-E slot on my board... nothing. Yet it still works in my other PC, and my old card works on my current PC. I have no idea what's going on.

 

[midiout]

I've now gone and tested a second PSU in my new computer with the 780 and it's till not displaying an image.

So the 780 works on my old motherboard with my old PSU, but does not work on my new motherboard.
My 560 works in both my new and old motherboard.

I can't come to a conclusion as to what part is causing the problem.

So far I've:

• 
  ■ made sure it was seated well and locked in
  ■ tried the 8x PCI-E slot on my motherboard
  ■ swapped out the cord for my power supply to new ones
  ■ tried a different power supply
  ■ tested the 780 on another computer and it works
  ■ currently a 560 in my computer is working

I want to say video card but it works on another computer.
I want to say motherboard but my old video card is working.
I wanted to say power supply after that, but changing the power supply has has no impact.