I found a work around as I had the same issue on a brand new HP elitebook 830 g8 where displays and everything was functional on USB 3.0 but display would not show up in USB-C (but peripherals and charge would work). To fix all I had to do was disable the thunderbolt controller in device manager, then hook up through USB-C where it then recognized the dock.

Unfortunately I need to leave Thunderbolt disabled to connect to the dock and can then re-enable but if it is enabled before connection it stops working like before. Hoping I can uninstall and reinstall the Thunderbolt controller software but so far not having much luck making it work without constant disabling.