Asus dark hero startup issue ?

[karlosfandango]

Hi all
I have a Asus Crosshair VIII DarkHhero ...with an AMD 5900X , 32gb of Gskils ram

Had a few times over last few months since recieving board where the system wont power on.
You press power switch on case and nothing .
You press power button on motherboard ...nothing ....and its lit up white ...all rgb is working ( on when powered off )
If i turn off PSU and back then power it back on ...system boots fine.
It can then be fine for say 4 weeks ...then happen out the blue again.
Was ok with old motherboard....so only things that have changed is MB and CPU.

Tried reflashing bios back to earlier version ...no different.
Had new graphics card since last time so rules that out.
Tried taking ram sticks out ...no difference.

Seems starnge how can run for weeks without issue ( but dont use it every day )

Im using an EVGA supernova 850W PSU.

Not major issue as all have to do is power off PSU and all good again ...but got to be something wrong.
Asus say sounds like something tripping PSU protection ...will have to try unpluging 24 pin and 8 pin cables next time , then plug back in to see if motherboard or psu .

Any help most appreciated.
Karl