I had the carplay connection difficulty. Found my phone VPN was the issue. As soon as I disconnected from the VPN (Proton VPN APP) I was able to CarPlay connect.
To the OP… did you by any chance rename the car’s network name? I did that after initially setting up CarPlay (successfully) and now cannot reconnect.
This is exactly what happened to me. I had to do a factory reset to recover from this.
However, since the factory reset I don't have the option to connect to wireless networks and when I try to access the app center I get an error that I should sign in with my porsche ID, even though I am signed in and my profile is active.