Are you not able to see the unrecognized video device in the device manager?
i had that same issue, but i only had to click on the unrecognized video device, install the driver from there and done!
I have installed windows on UEFI only mode. Its almost fixed! In device manager I can see the fifth GPU but with yellow icon. When I click on it to update driver, windows says the latest and best driver is already installed and nothing happens (GPU dont back to working mode).
I want to update driver to the latest but I'm afraid this causes new issues again. My current driver ver is 376.51 but it seems the latest is 384.76.