Child Page Featured Image / Thumbnail is appearing as a Blank Space

I have some php to list child pages, excerpts and thumbnails on the parent page. Everything is working great except the thumbnail. It’s appearing as a blank space instead of showing the image. If anyone could please help! This is so odd. You can see what I mean here.

<?php $children = get_pages(array('child_of' => $post->ID));

					foreach ($children as $child) { ?>

                       <div class="small-12 medium-6 large-6 columns end">
                       	<fieldset data-equalizer-watch>
                        <h3><a href="<?php echo get_permalink($child->ID); ?>"><?php echo $child->post_title; ?></a></h3>
                                   <?php echo get_the_post_thumbnail($child->ID, array(50,50)); ?>
                        <p><?php echo $child->post_excerpt; ?></p>
                        <a href="<?php echo get_permalink($child->ID); ?>">Read More...</a>
                        </fieldset>
                       </div>

<?php } ?>