Siri commands on CarPlay not working

When using Siri/Apple Intelligence through CarPlay, nothing happens or Siri responds saying sorry I’m having trouble with the connection. Yet if I use the handset it works perfectly and is on the screen in the car. This happens on all commands, making a call, set the destination on maps or play a song on Apple Music. This seems to have been since changing to iOS 26 a month or so ago.

what can I do to fix this, as I can’t touch the handset whilst driving.

the handset is an iPhone 15 pro max