Cannot get into bios

[xxbleedingspectrexx]

Rebuilding my old desktop, splash screen appears with “hit delete to enter setup” & “tab to display post bios message” mashing delete will not enter set up. Skips to the American mega trends screen & says “CMOS date/time not set! Will shut down in 15 seconds” I’ve updated the bios, reset the cmos battery & even replaced it with a brand new battery. I’m stumped... any ideas?

 

[ragnar-gd]

I had something similar, also went thorugh re-flashing, changing battery etc. In the end, it turned out the MoBo was damaged.
But it was a rather old, refurbished board, socket 775, and i was able to hand it back to the shop, so perhaps this cannot be compared.