We had a similar issue with our 2021Blazer. Check engine light would come on. Then transmission would not shift. Left my wife stranded having to get towed 3 times before it was finally fixed. First time they had it 10 days saying it was a software issue. Second time they had it 8 days and replaced a shift sensor. Third time 8 days again. I tried getting GM to buy it back. They said if it isn’t fixed on 3rd try that they would start the process of a buy back. They finally had a factory adviser look into it. It was a pinched wiring harness. We have not had any issues since the repair. But for awhile they we had serious regret. Lol