Motherboard flashes all lights once, then goes dark.

[jordanblk]

Motherboard lights flash once, then go out. I've disconnected the power supply and motherboard from everything except for the 24 pin and the cpu power, same problem. I then removed it from the case and placed it on the floor touching no metal, and it still does the exact same thing - the lights flash once, and then nothing. I've removed RAM and all other connections except for processor. Any help would be hugely appreciated.
Motherboard: Gigabyte z370 Aorus 5
PSU: Corsair RM750X
Processor: Intel i7 8700k

Update: Tested on a friends power supply, and had the same problem. Am I missing something really obvious here? Or maybe just a faulty motherboard?

 

[smorizio]

i cant get to the mb vendor web page right now. go to the web and see what bios rev is needed to post the new cpu. your mb may have an old bios on it and wont post. you can send it in to be updated or see if a local shop or a friend has an older cpu that will post.

 

[jordanblk]

i cant get to the mb vendor web page right now. go to the web and see what bios rev is needed to post the new cpu. your mb may have an old bios on it and wont post. you can send it in to be updated or see if a local shop or a friend has an older cpu that will post.

Checked the website and it said the motherboard is fully compatible with 8th gen processors. Just to verify, I popped in a 7700k I had lying around and again, had the same problem. I suppose that narrows it down to either a motherboard issue or a problem with my wiring. All I have in right now is the cpu 4x4 pin and the 24 pin main, that should be enough to keep the motherboard lit up right?