firefoxfx

Hi geoggg19,

You missed a ) on the first line, and the _ga cookie must been added in the plugin at the cookies used on this site section.
You can use this code: (did not test this)

add_action( 'wp_head', 'my_google_opt_out' );
function my_google_opt_out() {
  if ( is_allowed_cookie( '_ga' ) ) {
    ?>
<script async src="https://www.googletagmanager.com/gtag/js?id=GA_TRACKING_ID"></script>
<script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());

  gtag('config', 'GA_TRACKING_ID');
</script>
    <?php
  }
}