its a known issue with the Extreme 4 boards, they have cold solder joints on the ROG Chip between the last PCI-E slots, hence the mass posts of people needing hairdryers to start their boards. firstly i would try gently applying some heat to that area and lastly put some pressure on the ROG chip with your finger then try and boot it whilst pressing, if it boots that is your issue, i have fixed 3 Rampage extreme 4 boards by Resoldering the ROG chip back on as they were poorly soldered/pins aligned from factory, combined with crap solder and that area running quite warm due to the xx79 chipset linked to the vrm via heatpipe. however this requires some soldering knowledge and special tools, if you are out of warranty and your system still works using the above methods, take your board to an electrical repairer and have them resolder that chip or reflow if they are cheap, anyone who can work with SMC chips should be able to help you, hopefully this can save some older boards.
ASUS quality control on their high end boards is beyond a joke.
