Question ROG MAXIMUS XII FORMULA PCI Slot Seems To Prevent POST

[melchionda]

I'm building a new PC with the ROG MAXIMUS XII FORMULA. This is my first new PC in 12 years! I'm running an i9 10900K and have built a custom water cooling loop. When I turned it on for the first time with everything installed (CPU, Memory, Graphics card etc)and all fans plugged in. Unfortunately it didn't POST. The mobo would start to boot up and the Q Codes would quickly start to cycle. When it got to Code 19 it would start the boot process again. I narrowed the problem down to the bottom PCI slot. When I plug a card into that slot the system will not boot. When I plug the card into other slots it boots fine. Anyone ever see anything like this before?

 

[rgd1101]

full system spec? include make and model of the psu