Faulty sensor

Part of your motor insurance with Discovery Insure is the demand to fit a sensor to your vehicle. I have 2 cars on the policy. My one car’s sensor is operating well. However the other car’s sensor has been faulty since 9 June. It’s been changed but still didn’t operate. I’ve written to *** on four occasions. The first response said they had reset it manually from their side, but nothing changed on my side. The sensor still didn’t work. Two of the emails had responses explaining how to correct the problem from my side. I followed the instructions and even photographed each phase as it was done. Still the sensor didn’t work. The fourth email they have not responded to. I’m very disappointed as I think they’re a good company however there is a lack of knowledge or follow through with the sensors. Please advise