Hi Lee, I just had the same (or similar) problem. My motor was working but the backrest not - the underseat cable had bound up and stopped it all functioning. I replaced my cable and fixed my issue.
Your cable may have become loose, or may be broken.
There are three parts to this mechanism, 1. The motor, 2. a speedo type cable and 3. a geared reducing mechanism that essentially replaces your manual plastic spinner on the outside of the seat that would normally activate the backrest.
You get to it by unbolting the whole seat from the floor.
The motor is located underneath at the front of the seat, like a big D size battery. This has a speedometer type cable that simply plugs into it, with the cable and motor held in place with metal prongs.
When I replaced mine, as I was putting it back together, the prongs weren't pushed together hard enough, so the cable was allowed to slightly separate from the motor. By pushing the prongs in, it reseated the cable and all started working again.