Zbook 17 G3 will not power on

[britishtar]

TL; DR--Zbook running CentOS with built-in (i.e., non-removable) battery will not power on after repeated attempts, button-pressing sequences, and key combinations.

Hello!

My Zbook 17 G3 lost power in an interesting way--I was using a 200w brick (HP manufactured) and a 17.4 mm to 4.5 mm DC adapter dongle.  A small child and/or robot vacuum disconnected the power, but the dongle remained plugged in while the battery drained completely.  At the time of power loss, the machine was running the latest supported CentOS 7 linux kernel with all the default hardware drivers (except for the NVIDIA drivers, which I installed manually using the NVIDIA-provided packages).  Also, in case this makes a difference, I had disabled the "suspend on lid close" functionality by setting the HandleLidSwitch=ignore flag in /etc/systemd/logind.conf.

I've been unable to re-start the machine since it lost power.  I've attempted each of the following, multiple times:

1. Press power button

2. Hold power button for 2-3 seconds, then release

3. Hold power button for 15-20 seconds, then release

4. Plug in machine to power using 200w adapter (verify power LED lights) and attempt to charge for 30 mins - 12 hours, then attempt 1-3.

5. Plug in machine to power using 240w adapter (verify power LED lights) and attempt to charge for 30 mins - 12 hours, then attempt 1-3.

6. Press and hold "Windows" key + "B" key (also tried "Windows + V"), press power button for 2-3 seconds (also tried 15-20 seconds), continue to hold "Windows + B" until beeping and/or BIOS screen displays--but no beeps/BIOS screen ever occurs.

NOTE: (6) was suggested here: https://h30434.www3.hp.com/t5/Notebook-Boot-and-Lockup/HP-zBook-15-G3-won-t-boot-up/td-p/6724681

7. Sacrificed a chicken and prayed to the hardware gods.

None of these solutions worked.  The laptop shows no signs of life, other than:

(1) When plugged in, a solid white power LED indicator (right next to the 4.5 mm power connection)

(2) When plugged in using 200w adapter, a flashing white power symbol on the power button.  (this flashing light does not occur when using the 240w adapter)

Please help!