Hi @robbalista,
Looks like you have done the CMOS reset procedure. Have you tried an external monitor to see if that displays anything?
May be worth trying below now that you "down-dated" the BIOS.
For what it is worth this was on the HP site:
". . . recommend you to perform the following steps to isolate the issue and arrive at a fix:
Remove the battery. . .
Disconnected AC adapter from the laptop.
Press and hold the power button for 15 seconds.
Reconnect the battery and plug the AC adapter.
F6 + Power Button
CMOS Rest (? reset?)
combination of windows button and letter 'V' then push the power button ones and release the windows and letter 'V' after 5sec."