Why might my car's microphone stop working with CarPlay?

Why might my car's microphone stop working with CarPlay?

The car’s microphone works for its built-in voice commands. But when I press and hold the button on the steering wheel to send a message to Siri it doesn't hear anything. The little pulsating blue dot appears on the CarPlay screen, so it's listening, but the request just times out.

My phone’s built-in microphone works, just not when using the car's microphone when in CarPlay.

I can play music from my phone via CarPlay.

It works for my wife's iPhone, same model and version of iOS

it stopped working for me in both of our cars, so it's not the cars or cables.

I have restarted my iPhone.

Any suggestions?