GPU doesn't display, black screeen, replaced mobob and cpu

[stumple]

I just replaced my mobo and cpu. The pc runs fine when the gpu isn't in place, but when I put the gpu in the pc starts and runs, but the screen is black. Even if I have my monitor plugged into the onboard graphics it still doesn't display. The gpu isn't defective since I was just using it yesterday before I upgraded.

GTX 560
z97 pro4 mobo
intel i3 -4370
775w psu

 

[stumple]

So far I've tried updating the BIOS, making sure the primary is set to PCI-E, and making sure the gpu is seated properly and has power.