No video output no matter what I do

Not sure if this site is the right place.
I got a new motherboard and a new cpu recently. For whatever reason, there is no video output on either the graphics card or the on-board motherboard video.
I changed the HDMI cable, ive changed the monitor, I used the graphics card in a different PCIe slot. I’ve cleaned the ram, the ram slots, I even changed the power supply cord. I spoke to a friend who is a computer engineer, and I also spoke to a Geek Squad member at a Best Buy and they were both dumbfounded. I’m sure the RAM is compatible, I’m sure I installed the CPU correctly, I’m sure it’s not an issue with the graphics card or the monitor or the HDMI cables. What else could it be?