iphone 12 says, "no internet connection", when I'm in my car.

Hello!

So, I'm driving and my wife is trying to use various apps on her iphone12. It gets either slow, or non responsive, and gives her a message, "no internet connection". Of course there is no internet connection. We are in the car! We are not at home or using a wifi anywhere, because we are in the car, on the road. Why would her phone be non responsive when it should be using cellular, as it typically does?