I was experiencing the loss of corded CarPlay with my 16 pro max and running 18.3.2 but it was intermittent then stopped all together. I tried to buy a wireless CarPlay adapter off amazon and same thing worked for awhile solid, sporadic then completely nothing. So I said f it I went years without it and use Bluetooth to do everything. My phone connects thru Bluetooth to my car but sometimes it will say it’s connected and play but nothing comes over the speakers. This I found I needed to forget the device on my phone and car and reconnect everything was the fix (tried various combos of forgetting, disabling and power cycling).
A friend’s 14 was acting the same as mine, cables would charge and CarPlay worked intermittently on my car for corded CarPlay and the wireless adapter.
Well today $115 later the dealership told me nothing was wrong and one of their techs had a 12 on 18.3.2 that works but the 14,15 and 16 that were tried were not functional running that. They would not connect to the wireless adapter because it was after market :-/ but after the update and 2 days at the dealership I was able to connect to wireless CarPlay. If it wouldn’t have worked I was about to go to Apple and have them revert my phone back three iOS versions so I could have CarPlay back. So fing frustrating!