That is weird, I did the same thing as you did. I have a 2020 Custom Trail Boss with the IOR stereo and changed the single USB to the dual USB and it works fine. I can play XM while having Car Play on screen. I can even have both my wife’s and my phone connected at the same time and play from one or the other. After you connect your phone does it bring up Car Play automatically? I do notice that it will go to what you had selected before you got out of the truck last time whether that is you listening to your phone, radio or XM. Next time you plug your phone in and it goes to Car Play, hit your home button, tap the XM app, select your station, then hit the home button again and tap on the Car Play. Usually that allows me to listen to XM while having the Car Play up when I’m using maps. I hope that helps some.