Question Motherboard flashes on then off ?

[Vela17]

I just tried to build a pc but when I flip the psu switch on, the motherboard lights flash for half a second only and then they stay off. the gpu has a small light by its power connector that stays on. I had the same issue before so I returned the motherboard for a new one but I still have the same issue. I already tried booting up with just a cpu, motherboard and psu with one stick of RAM and still get the same issue. Would a bad cpu be the culprit or is it possible that I somehow short circuited both motherboards?

My specs are
gigabyte z490 vision d,
i5 10600k,
corsair vengeance LPX 16gb x2 @3000mhz,
and corsair rm 850x psu

 

[rgd1101]

plug in both the 8pin and 4pin cpu power?