Tigertrout970

I have a 2019 sierra 1500 slt. I had some new winter tires put on back in the fall and the rear driver side tire quit reading pressure. Eventually all the tpms sensors quit reading and I got the notification to check tpms system. I ordered a relearn tool and went through the proper procedure to relearn since I had new tires installed. I got can a reading from 3 tires, but the rear driver side won’t relearn. i ordered a new sensor, had a mechanic install it, and they have the same issue. They claimed the new sensor was working when they checked it. That one tire (even with new sensor) won’t relearn. Any advice on why this one tire won’t work? Thanks. edit: i should add in that when I turn on the truck the tire pressure light flashes for a bit before it becomes a solid light.