Siri not responding on iPhone 16 Pro Max

As title says, Siri is not working. It only works if I press the side button, not by me saying "hey siri" etc.

I have turned siri off and back on again and done the 5 phrases to set it up and still nothing. I have changed the language, changed the voice, changed to prefer spoken response' and still nothing.

Obviously on IOS18.

Has anyone else had this issue because it is driving me mad. £1,400 for a phone and it doesn't work properly!