Dell XPS 9550 TB16 Dock

Greetings

I am having difficulty with Windows 10 not recognizing my thunderbolt dock from a cold start. Here are the hardware/OS details:

XPS 9550
TB16 Thunderbolt Dock
Windows 10 Pro 1903 18362.388

I have 2 Windows 10 installations. An OEM that came with the machine and a retail version which I purchased. The retail version recognizes the TB16 dock before login. The OEM version does not. So with the OEM, anything attached to the dock is not functional. The only way I am able to use the items attached to the dock, is to use the built-in keyboard, open device manager and scan for hardware changes. The dock is then recognized and all items are functional.

Did I inadvertently change a setting that prevents Windows 10 OEM from automatically recognizing the dock? I should point out that this issue starting occurring after the cumulative update in September. However, after that update, I was able to overcome the problem by starting the machine with the power button on the dock (I have to option to allow the dock to wake the computer activated in BIOS). Before using the dock power button, the dock was not recognized by either the retail or OEM versions.

I've probably over-explained the issue here. Sorry. I just wanted to present as much detail as possible.

Any and all assistance is most appreciated.

Graham

The Dell manual (linked below) shows detailed setup in Windows. If something was missed that could be the problem.
Dell has a forum that is good for getting specific Dell assistance.

Dell Manual

Dell Community XPS Laptop Forum Section

Thanks fireberd