I am not convinced that the pretensioner deployment has anything to do with this with regards to a software issue, although it is possible the deployment did some damage to the underside of the seat. It is tempting to assume a poor connection from removing and installing the seats. It may be worthwhile to check the large under seat connector for any bent pins in the male side of the connector.
I checked the repair manual, and here is how the seat HVAC system works: "The driver and passenger heated and vented seat switches are located near the HVAC controls on the center stack. The BCM is the heated and vented seat system master. It monitors heated/vented seat switch activations to determine user requested operating mode. Based on the requested operating mode, the BCM sends a LIN Bus serial data message to the front seat heating control module how to drive the self-regulated heating pads or ventilation motors. The BCM also controls the indicators used to provide the operator with feedback as to the operating status of the system. With each press of the switch, the system will cycle through High, Medium, Low, and then back to Off again. The BCM also controls the seat temperature and mode indicators, via the serial data line, used to provide the operator with feedback as to the operating status of the system."
So, the BCM and front seat heating control module are the other likely issues. I would be interested in the front seat heating control module. I pulled up the diagram for where it is located below. This is located under the passenger seat (controls both the driver and passenger seat). I would start with an inspection of this. Look for damage to the wiring, connector, the module itself including any burnt material...
https://ibb.co/jVQG6wr
