I have a ‘20 which is wired CarPlay. I have had issues since new with connecting. If I am lucky 90% of the time it will connect first thing of the morning. But if I make a stop 10 minutes later it will not reconnect. Big bummer if you are starting on a long trip.
I did notice last winter when leaving work and it was cold during the day, CarPlay would connect 80-90% of the time. As soon as it started to warm in the spring, that dropped to about 10%.
I am starting to believe it is a USB hub issue that doesn’t connect well when it heats up. I have been to the dealership with it 3 times, 2 of which they told me there was no issue or it was my “cheap” (Apple brand) cables. When I opened a new Apple cable and showed them it wouldn’t work, they called GM tech support but never got a resolution to this issue.
I have come to an “if it works fine, if not, fine” conclusion. I just remember that my first new truck (‘80 K10 Silverado) didn’t have that issue, but I didn’t have a cell phone either.