First and foremost, what’s very important to know is that Apple has already released fixes for this issue. iOS 13.4 resolved the bug, and several iPhone 11 owners confirmed on Apple’s forums that installing this release brought things back to normal, with CarPlay now running correctly.
But if you’re among those who are still unable to launch Apple’s CarPlay on the iPhone, and you come across the same problem as these people on Apple’s forums and on reddit, the first you need to check is whether your smartphone is running the latest iOS version.
To do this on the iPhone 11, go to Settings > General > Software update and install any available updates.
If the iPhone is already up-to-date, you need to check if the car is already paired with the iPhone. This is an issue that’s mostly experienced on devices that are restored from a previous backup (if the iPhone 11 user owned another iPhone before) and thus the Bluetooth settings have also been migrated.
If the car is already paired with your iPhone, delete it and then reconnect the iPhone to the car so the whole thing is restarted. Some say that deleting all paired Bluetooth devices helped too, but this is a rather inconvenient workaround that you should only try as a last resort.
If this doesn’t work, you also need to check your head unit’s settings and remove all the phones that are paired. This should force it to forget the iPhone and then restart the process from scratch.