It has taken a long time to complete my build, finances would not let me purchase all the components at once.  System so far:
EVGA Z790 Dark Kingpin;  EVGA RTX 3090ti FTW3 Ultra; i9 13900KS; Corsair Platinum DDR5 64GB 6600MHz;  Corsair HX1200i PS; Full Custom EK Waterblocks Loop in Lian Li 011 evo XL case with front resevior, 2 X360 Radiators and 10RGB fans. 
The S*%T hits the fan with EK, EVGA seems to be winding down - bit demoralised at this point.
Booted for the first time today and no post (Code 97) - checked all cabes, connections, seating and tried again - same result.
Any help/suggestions welcome TIA.  

Try to update the bios. I can't login on desktop to help with links (there are threads here with full instructions), but basically you can download the latest bios, put the file on the root of a USB drive (change the file name for this process) and force the motherboard to update the bios without booting first. Also, instructions can be found on page 105 of the user manual.

I don't remember if the Z790 supported the 13900ks on the first bios version, so I would start with that.

If you haven't looked at this thread yet, you may find some useful info here ->  https://forums.evga.com/BIOS-for-Z790-DARK-KNGPN-113-CLASSIFIED-111-Features-Bug-fixes-m3601626.aspx
 

Maybe checkout this thread… https://forums.evga.com/P...ingpinHC-m3546013.aspx

hey bro, did you also put the cpu in the right orientation? Z-790 kingpin has the socket turned 90 degrees. i payed extra attention to that on my Build i also own a Z-790 dark Kingpin

Thanks for your response and suggestion:  I was extremely careful with orientation and details oif the build - it is a full custom waterloop and I certainly did not want to F it up.  I am going to try to update the bios later. 

Have tried updating bios (both 1.15 and1.20) some progress but sticks at A6 code have stripped system down drained it and flashed bios without CPU etc. Cleared Cmos going to try booting in safe mode (learning a lot but feeling I have bitten off more than I can chew (old fart syndrome lol)).