Plugin not working with theme

The theme I’m using is not responding at all to this plugin. Here’s the PHP that seems to currently be handling generating the excerpt. Is there something here that is blocking this plugin’s ability to work?

// Excerpt "more" text settigns
function new_excerpt_more() {
  if(get_post_format(get_the_ID()) == 'link'){
    return '...<div class="read-more-link"><a href="'. get_field( 'external_link' ) . '">' . __('Read More', 'pluto') . '</a></div>';
  }else{
    return '...<div class="read-more-link"><a href="'. get_permalink( get_the_ID() ) . '">' . __('Read More', 'pluto') . '</a></div>';
  }
}
add_filter( 'excerpt_more', 'new_excerpt_more' );

function os_excerpt($limit = 16, $more = TRUE) {
  if(!$limit){
    $limit = 16;
  }
  if($more){
    return wp_trim_words(get_the_excerpt(), $limit, new_excerpt_more());
  }else{
    return wp_trim_words(get_the_excerpt(), $limit, "");
  }

}

function os_quote_excerpt($limit = 16){
  return wp_trim_words(get_the_excerpt(), $limit, '...<span class="quote-read-more-link">' . __('Read More', 'pluto') . '</span>');
}

https://wordpress.org/plugins/advanced-excerpt/