Combo van passenger sliding door stuck shut?

My 2008 combo 1.3 cdti crew van sliding door behind the driver won't open. All the other doors work OK with the remote. I have removed the inside door panel and checked the control wires all are attached and are free to move, and there is no damage to any cables. When I operate the remote central locking key there is no movement or sound on this door. Is there a solenoid that releases the catch and if there is.... where is it? and how?.... etc etc etc