Elitebook Laptop not switching on

[DeanoWWFC1]

Hi,

After a period on non use my laptop does not want to power up.

All is ok with power adaptor as when plugged in I get a flash of LED’s from keyboard and power light.

tlTried the power button pressed in for a period of time but nothing.

any help would be appreciated as I’m losing it now haha!

[RickMtl]

I just resolved a similar issue, check out my name and/or Elitebook 840 G5.

I had to disconnect both the CMOS and regular batteries, then press and hold the power button, then with the batteries disconnected, I attached the A/C and then the laptop booted up.

I had to disable hibernation and create a shutdown.bat file (with commands for a full shutdown) and use that to power off the laptop.  If I used the regular Start > Power > Shutdown, after a few hours, it would never power up unless I opened the case, unplugged both batteries, held the power button, then connected the A/C (with both batteries still disconnected.

It drove me nuts for over a month until I found a work around.  I also would recommend trying different BIOS version as that can be the problem too.

[DeanoWWFC1]

I did manage to sort this by using the power adaptor and disconnecting the battery. 
Root cause was a damaged battery in the end, so all resolved now

thanks for the reply