CarPlay

Try a "forced" restart of your 12p, using these gestures:

Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the side (power) button. Only when the Apple logo appears (it might take 10-20 seconds), release that button (ignore all other screens that might appear, the one with the "slider" to turn the device off included).

If the issue persists, contact Apple Support, using this link:--> Get Support

Or, check: Settings>ScreenTime>Content&Privacy Restrictions>Allowed Apps... Carplay MUST be set to "Allow". When done, restart your iPhone.

Regards

Giulio