carplay no sound after OS15.7 update

I have been using Carplay without any problems in a Mercedes Benz B200 until I updated my iphone XR to OS15.7.

Since the update, I cannot get any sound from Carplay when using google maps, playing music, using siri etc. Also when I first start google maps, I just get a blank screen. Once I search for a location, it goes ok.

I can make and receive phone calls ok.

I have tried sorts of resets and restarts as suggested on other threads but none give me my sound back.

I generally connect to the phone by wifi but connecting with a usb cable does not make any difference.

Can anyone suggest what is wrong and if a solution is available?