HP zBook 15 G3 won't boot up

[JorgeATT]

Battery ran out and laptop shut down. Plugged in power supply, won't boot up. Tried holding down for 15 seconds or longer, still no boot up. This model does not have a removable battery.  Help!

[CF4]

Hi

This is what you have tried?

Please 1st try a Hard Reset

Press and Hold the PWR off button for 4 seconds to force a PWR off.

Unplug from the wall.

If you see a battery compartment door, your computer has a removable battery.

Remove any removable battery.

This is valid for most notebooks;

Press and hold the power button for 15 seconds to complete the reset.

Re-insert any battery you removed.

Next I would try repeatedly pressing the ESC at power on.

Then

TROUBLESHOOT startup errors on models with UEFI diagnostics
https://support.hp.com/us-en/document/c01442956?openCLC=true

Finally in desperation...

https://support.hp.com/us-en/document/c02693833

Turn off the notebook.
Plug the notebook into a power source using the power adapter.
With the notebook off, press and hold the Windows logo key and the B key at the same time (WinKey +B).

NB: On some notebook models, it might be necessary to press and hold the Windows logo key and the V key (WinKey +V).

While pressing those keys, press and hold the Power button on the computer for 2 to 3 seconds, and then release the Power button but continue to hold the Windows logo key and the B or V key until the HP BIOS update screen displays or you hear a beeping sound (usually 8 beeps).

If in doubt pease ask.