Single post comment template not working

Here’s 2 solutions i tested:

Try adding support for comments in your custom post type code

'supports' => array(  'comments' ),

You could also use add_post_type_support

add_action('init', 'wpsites_comments');
function wpsites_comments() {
    add_post_type_support( 'events', 'comments' );
}

Code Source