www not working

I’m new to all this so sorry if this is a silly question.

If I visit my site without the www it works fine, but with the www I get an error “server IP address could not be found.”

I followed the tutorials and my file: /etc/nginx/sites-available/animalrescue.co.uk looks like this:

server { listen 80; listen [::]:80;

    root /var/www/animalrescue.co.uk/html;
    index index.html index.htm index.nginx-debian.html;

    server_name animalrescue.co.uk www.animalrescue.co.uk;

    location / {
            try_files $uri $uri/ =404;
    }

}

Am I missing something?

thanks