Same issues with all the others on this thread. Discovered a possible fault. My Surface Dock (and its USB Ports) will work perfectly when connected directly to the detached Screen/Clipboard. By 2 Docks work perfectly with my SP4, but both have the same issue with no USB functionality when plugged into the Surface Book Keyboard.
So it seems to be a fault with the Surface Book Keyboard (which houses the Dock Connector Port and has its own USB Hub). Possibly Hardware, but mine worked perfectly for a year until last months updates. So likely a driver, firmware or other software issue with the Keyboard component of the Surface Book, not the Dock.
I think blaming the Dock has been why this has not been solved. MS, or someone, should look at the Keyboard.