HP ProBook 640 G8 does not see displays on HP USB-C G5 Essential Dock

[ChrisW4170]

HP USB-C G5 Essential Dock (72C71AA)

Two HP laptops:

*    HP EliteBook 840 G8 (3G0D8PA#ABG)

*    HP ProBook 640 G8 (36L68PA#ABG)

Both devices see the USB devices plugged into the dock (keyboard and mouse).

Both devices are up-to-date Windows 10 Pro or Enterprise.

The EliteBook sees both DisplayPort monitors connected to the dock and drives them correctly (both 1920x1080).

The ProBook sees no external monitors connected to the dock (DisplayPort or HDMI)

The ProBook is explicitly listed as compatible here:

https://pcb.inc.hp.com/webapp/#!/au-en/contents/2100620730?type=L&hierarchy=F&status=L&status=O

The ProBook has (as best I can tell):

* Latest Windows updates including all optional updates (include HP firmware)

* Latest of everything from HP installed in the way of BIOS and drivers.

* Latest Synaptics DisplayLink driver

* Latest Intel driver including the Iris Xe graphics driver released 28 Feb 2023.

The dock firmware has been updated.

All installed over the last couple of days by our corporate IT support.

Any advice?

[ChrisW4170 · Accepted solution]

Success. 

TL:DR. The laptop  just needed a long hard look at itself in the room of mirrors.

Investigating why the HP USB-C G5 Essential Dock device appeared under a USB 2.1 hub, I stumbled across this forum post

My USB Type-C port not working

The solution offered in there was: Shutdown, unplug all external devices, press and hold the power button for thirty seconds.  Restart the machine.   Took a long time to restart; probably reconfiguring everything from the ground up without a cache.

This worked (much to my surprise) and the displays sprang to life.