Hi:
I am looking at the picture of the motherboard below...
https://support.hp.com/us-en/document/c04439095
There are two jumpers.
One clears the CMOS and one clears the P/W.
Usually you have to shut down and unplug the PC.
Move the P/W jumper over one pin, plug in and turn on the PC.
The P/W should now be cleared.
Then shut down, unplug the PC and replace the P/W jumper to its original position.