Another common issue that users report is a blank/unresponsive in-car display when they plug their iPhone into the car to be used with CarPlay. Now while this could be a sign of a bigger problem with the unit itself, it’s worth trying a few things first before you call your car’s manufacturer.
First off, restart your iPhone and try plugging it in again. If that doesn’t work, try using another USB port if possible, or using a different Lightning cable in case the one you’re using is damaged.
Of course, it could also be due to the firmware of the car itself, especially if it happened around the time of a new CarPlay software release. To update the car’s firmware, consult your manual.