New build, sometimes POST

[System123]

I recently completed a build with the following specs:

Gigabyte X99 UD4

Intel Xeon 2620v3

Corsair Ballistix 2400MHz DDR4 4x8GB

Samsung NVMe 1TB SSD

Gigabyte Nvidia GTX 1080

 

Initially the PC booted fine, but I noticed only 3 of the 4 RAM sticks were being picked up. So I shut it down and reinstalled all the RAM. Now the PC will not POST, on pressing power the case fan and CPU fan spin up, but none of the motherboard or back panel lights come on and I the display has no signal. Also none of the USB ports have power. It is as if the board just gets stuck booting.

 

If I remove all the RAM and reboot the PC, then the motherboard and back panel lights come on and USB has power but I never get a BIOS screen. Installing a single stick of RAM leads to the PC occasionally booting, I need to restart a few times for it to boot. I have removed all unrequired HDDs, and PCIe modules and still nothing. I tried swapping out the RAM or using different slots but I still only occasionally get the PC to boot with 1 stick of RAM.

 

Any ideas? Is the motherboard fried?