Since none of the other mods are helping (yet), I'll try my best to see if I can help.
So to make sure I have everything correct, the GTX 960 doesn't work in the main computer, but works on the other two PCs correct?
If so, make sure your BIOS is up to date. Go to ASrock.com and check for a BIOS update. You'll have to go into your own bios to see what bios number it has.