Thanks Barb, running the dock updater with the dock connected directly to the clipboard (no keyboard attached) made no difference at all - still the same error message and instruction to power cycle the dock.
Here's the copied data form the Surface app you requested:
Name: ------
Serial number: -----
SKU: Surface Book i5
Version Information
Embedded controller: 90.2098.256.0
UEFI: 91.1926.768.0
Touch: 51.250.94.0
Wi-Fi driver: 15.68.9112.23