If a radio unit was installed that is capable of Apple CarPlay, and Apple CarPlay does in fact work... yet suddenly Apple CarPlay quits working, It is imperative to check the Apple CarPlay settings in the iPhone if the iOS update was installed before it suddenly stopped working. There have been several times over the years where an iOS update is sent out by Apple, and Apple CarPlay functionality suffers. Sometimes this is a bug, where another update will correct it, or the settings in Apple CarPlay were changed by the update.
This link to Apple Support provides troubleshooting tips for Apple CarPlay.