Heated seats do include both the bottom and back separate heating elements, unless they are after market ones. If you have the switches in the button console area then I would think OEM - so both panels. Build sheet would verify for sure. Put your VIN in this link, and paste it into your browser. Will give you your build sheet for your truck (Example VIN on this sample link is:3C6UR5FL6FG603312 - just put yours instead)
Another thing to check is if the 2 connectors (one to back, second one to bottom heating panel) are connected right/fully. They're located on the back side of the seat, under the bottom just a little bit. You could disconnect and reconnect just to make sure the connections for each one are fully seated. You'll see where one goes into the bottom cushion and the other wire goes up for the back one.
Fuses all good? (tbh- not sure if there are separate fuses for driver side vs passenger side, just trying to cover all bases in case it's a simple fix) - maybe others will chime in that have worked on drivers heated seat issues. My experience so far is what I've researched on Ram trucks, and dealing with not working in other vehicles as well as adding after market heated seats in a couple other cars.... But just trying to help here.
From what I've read thus far (cause I've got a rear drivers side bottom panel that's out right now - but no riders that will need it so waiting to replace for now), it's the bottom one that goes first in most/many cases due to getting pressure on/off from driver getting in/out of the truck. From all seasons being used.
