[Plugin: Disqus Comment System] Custom disqus_identifier not changing properly.

I have several pages that are all part of the same topic, and I would like them to use the same comment thread on Disqus. I am using the following code to pull the custom identifier from a custom field:

<?php
//Attempt to get identifier
$disqus = get_post_meta($post->ID, 'disqusid', true);
//if isset & not blank else use $post->ID
$disqus = (!empty($disqus)) ? $disqus : $post->ID;
?>
<script type="text/javascript">
var disqus_identifier = '<?=$disqus?>';
</script>

The code is displaying the value from the custom field correctly, however, Disqus is still using the page ID as the identifier when I inspect the page code. Meaning each page still uses its own comment thread.

I have tried placing the code just before the comment_template call, inside the header.php, at the top of the page template, and in the footer.php file. None of them seem to make a difference.

I’m not sure what else to try, and feel like I’m missing something simple. I appreciate any help!

https://www.ads-software.com/extend/plugins/disqus-comment-system/