Did you replace CMOs battery w a new one?

Try clear cmos by motherboard CLR CMOS jumper.

Re：unplugged/replugged CPU pin

did you remove cpu from LGA socket and reseat it?

yes, i bought fresh cmos batteries and replaced it

yes, i cleared cmos with jumper

yes, i reseated the cpu

No need to take risk to reseat cpu unless you want to upgrade it. When cpu is reseated there is risk of bending socket pin if not careful, which would render board not POSTable.  If curious look at cpu socket with magnifying glass to inspect. Upload a close up high res picture of cpu socket if you can.

It appears that i cannot upload a picture.

But i have taken a closer look at the socket with a USB-microscope, and it did appear to be ok (no expert)

I have disconnected from the motherboard:
-power on/off switch
-intruder alert
-internal speaker
-Sata cables
-power cable to DVD/HDD/SDD
-CPU fan

Only thing that is connected are:
The 6 and 4 power pins, RAM and CPU that is connected, and still the problem persists.

Think we can rule this case as a bad motherboard

Thank you so much for your help and time

have a beatiful day