There are no solenoids in Volvo trim systems, they use relays, and low oil would not prevent the motor from running.
I would pull the relays and check the connections for corrosion. If they are clean, you probably have a bad relay. Yes, they can click and still not work.
It also takes both relays to go either up or down. Below is a wiring diagram to help you figure it out. You can pull the relays out and check the sockets with a test light or meter. If they test OK, they you probably need a relay.
PS Green = down, blue = up
Does anyone have any info on how to get a new wiring harness for this. mine just burnt up, and every dealer I called said they don't make it anymore