common problems on volvos and you could do a search here to find the solution. It basically involves taking the back of the seat off and accessing the mechanical cable which turns the crank to position the seat.

First see if your motor is spinning.. by sitting in the back seat of the car behind the drivers seat to the right mid side of the seat where the motor is located.

If you hear the motor then its the mechanical cable.

If you dont hear the motor then its the motor or the electrical/ electronics under the seat. Make sure none of the electrical connections are loose.

You can temporarily get the seat in the right position by removing the back cover of the seat and taking the place the cable is connected to. (the plate has two screws)