RSS Feed Shows NULL When Asking For Thumbnail

I am pulling in posts from separate WP installs on separate URLs. I have everything I want except for the thumbnail. My theme supports thumbnails but when I ask for the thumbnail it is showing me NULL. Anyone know why this may be happening? When I var_dump($item) it shows NULL for my thumbnails. All my posts on that sep. URL do have a featured image.

functions.php

add_theme_support( 'post-thumbnails' );

The RSS Page

?php
  include_once(ABSPATH . WPINC . '/feed.php');
  $rss = fetch_feed(PATH_TO_MY_URL);
  if(!empty($rss)):
    $maxitems = $rss-get_item_quantity(4);
    $rss_items = $rss-get_items(0, $maxitems);
  endif;
?

?php
      if ($maxitems == 0) :
        echo 'No News.';
      else :
        foreach ( $rss_items as $item ) : ?

          div class="post-block"
            figure
              a href="#"
                ?php
                  if ($enclosure = $item-get_enclosure()) :
                        echo $enclosure-get_thumbnail();
                    endif;
                ?
              /a
            /figure
            h3 class="mbs"a target="_blank" href="?php echo $item-get_permalink(); ?" class="link-color-1"?php echo $item-get_title(); ?/a/h3
            ?php echo $item-get_description(); ?
            a target="_blank" href="?php echo $item-get_permalink(); ?" class="btn mtxs btn-sm btn-color-3"Read Full Article nbsp;i class="fa fa-angle-double-right"/i/a
          /div

        ?php endforeach; ?
      ?php endif; ?