What Does It Mean if I Have to Hold the Power Button for ~20 Seconds Before I can Turn on My ZBook?

[innocrex]

Problem:

My HP ZBook (G8) always needs to have the power button held for a long time (~20 seconds or so) before it will respond to the power button and boot up.

Key Details:

The battery is always fully charged when once it boots, and it works (and doesn't work) the same way whether using the battery or AC power.

The only light is on the ethernet port; pressing the power button for less than five seconds has no observable effect whatsoever.

Pressing for more than five seconds turns the ethernet light off briefly, but then it comes back.

If I keep holding the power button, the ethernet light then blinks, and eventually Caps Lock and the power button will blink.

It is around this time that I usually have success if I try to release the power button and then press it again, which sometimes works (maybe 50% of the time).

(I think that I haven't quite figured out the exact timing yet on the long press as the light flash.)

I am hoping to understand why I cannot simply press the power button briefly or for a few seconds in order to successfully boot the system.

Other Details:

Note that the PC consistently functions fine for me while running, and it can perform a direct restart from a running state without issue.

Moreover, I never have to remove the battery (and have never tried to do so), nor do I notice a difference if peripherals (power adapter, ethernet, USB -- any combination of those) are connected or disconnected.

The PC is quite new (at least to me it is; it was issued to me recently).

I am merely booting from disk (SSD), and once I get it to actually try to boot, it goes through just fine.

Thanks in advance for any insights.