I had a problem where the passenger side would only go down from the driver's side. This was due to a broken wire in the door opening 'A' pillar loom / plug&socket. Checking the wiring with a meter and Haynes manual is the obvious answer. It is also possible that the motor electronics have failed.
Does the global open/close work? - that would prove if the motor electronics is OK.
Does the global open/close work? - that would prove if the motor electronics is OK.