my guess
the passport ultra does not have it’s own power source
WD being a very low power device
may not be able to provide the power to wake it back up over a usb connection only
it’s generally known that if a hdd does not have it’s own power source, it might not function correctly with a WD media player, or at least that the long standing observation from prior devices
additionally there is an official list of supported devices, including hdd’s, and the passport ultra is not listed
