Unable to get comment rss feed working

I burned a post feed via Feedburner/Feedsmith and it’s working fine. But I’m unable to get a comment feed to burn. FB returns the following error:

The feed URL you entered is: https://fitnessintuition.com/wp-commentsrss2.php
We could not find a valid feed at that address.

When I click the link to validate the feed, I get the following error messages:

Sorry
This feed does not validate.
Server returned HTTP Error 404:

In addition, interoperability with the widest range of feed readers could be improved by implementing the following recommendation.
line 12, column 1: Missing atom:link with rel=”self”

I’m wondering if there’s a problem with the wp-commentsrss2.php file. Here’s what the file looks like when I open it in Dreamweaver:

<?php

if (empty($wp)) {
require_once(‘./wp-config.php’);
wp(‘feed=rss2&withcomments=1’);
}

require (ABSPATH . WPINC .
‘/feed-rss2-comments.php’);

?>

Thanks for any help!