dose the motor run at all in front or back positions??

It may be your seat back cable, there is a sqaure "male" end of the cable on the motor side and the gear side that both goes into a "female" end. over time
due to expansion and contraction the cable floats out of the female end just
enough for it not to turn, its kind of like a bike cable but with square ends
on both sides

goto volvospeed.com look for bay13, there is a step by step repair
in the mean time you may be able to click back click by click,

the repair takes a couple hours but can be done by a do it your selfer.

hardest part is removing the hog clips that hold the seat on.

do a search on this site "seatback cable" tons of info

I end up cutting 10mm off of the cable housing which lengthed the cable
that forces the "male" end deeper into the "female" ends.

you will need to remove the cable just slide the cable part way out
of the housing, heat up the end cap with a lighter, slid the cap off
than clip the plastic black housing 10mm or so than slid the end cap
back on, than I took a dremel/grinder to both ends to sqaure up any
rounded edge do to stripping.

If you try this repair your self make sure the motor works first,
remove the cable from the gear side and reach around see if the
sqaure end rotate.

good luck