title: my wordpress thumbnail does not display/ html output is not what I need
body: <p>I have created a custom post and I am trying to display its elements. Title works fine.
  Thumbnail does not.</p>
  <p>PHP:</p>
  <pre><code>&lt;?php
        $args = array( 'post_type' =&gt; 'course','post_status' =&gt; 'publish','posts_per_page' =&gt; 3,'order' =&gt; 'ASC');
        $wp_query = new WP_Query($args);
       
        while ( $wp_query-&gt;have_posts() ) : $wp_query-&gt;the_post();?&gt;
          &lt;h1 class=&quot;home-header aligncenter&quot;&gt;&lt;?php the_title(); ?&gt;&lt;/h1&gt;
       
         &lt;img src=&quot;&lt;?php echo  wp_get_attachment_url( get_post_thumbnail_id( )); ?&gt;&quot; alt=&quot;&quot;&gt;
       
  &lt;?php endwhile; ?&gt;
  </code></pre>
  <p>In HTML while I see no image in the source code I get the following:</p>
  <pre><code>&lt;img alt=&quot;&quot; data-src=&quot;correct-file-url&quot; class=&quot;lazyload&quot; src=&quot;data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==&quot;&gt;
  </code></pre>
  <p>When I delete the src=&quot;dara:image.... in the browser the image renders correctly.</p>
  <p>What am I missing?</p>
  <p>Thank you!</p>