bent cpu pins?
I also have experience with bent cpu pins before. That also possibly causing OP's problem.
OP you should check!
If no screen, you check if you have plug in the extra 2 molex and 1 sata needed to power the board.
Basically, that extra Molex used as GPUs extra power (PCIe bus), but I found some thread before with almost the same problem and solved with that (two extra Molex on board).
@OP
Have you tried to reset CMOS? Unplug and re-plug memory (RAM), boot your system without HDD (SSD) and plug the monitor at the onboard graphics.