Heated seats the driver seat on our 2002 jeep grand cherokee will not heat. passenger seat works, what could cause seat to stop working

Likely, the heating element in the seat has failed. The reason is simply that the drivers seat is in use more than any other seat in the vehicle. You can check continuity of the element with an ohmeter across the seat side of the heater connector. Check for power at the harness side with a volt meter. If there is power but no continuity, heater element has failed. Personally, I'd probably just live with it but you can either attempt to install a new heater element or if you can find a similar seat in a salvage yard, just buy it and put it in! (whole seat probably costs less than the element!!!