Strange issue please help

[Azazel Ashbighy]

So my computer isn't displaying out my graphics card it detects it's there the drivers are up to date the gpu works when I put it in my gf's computer I plugged her gpu in and it didn't display out , I flashed the bios I replaced the ram with some spares if cleared and reinstalled windows I'm thinking it might be the motherboard but I would like suggestions before resorting to making a purchase