Didn't work

So here is my code I’m currently using for pulling category from custom custom taxonomy. Everything else seems to work but the featured image ??

<?php

//get the current term from the header

//then set the args for wp_list_categories
 $args = array(
    'child_of' => $term->term_id,
    'taxonomy' => $term->taxonomy,
	'hide_empty' => 0,
	'hierarchical' => true,
	'depth'  => 1,
    );
$categories = get_categories( $args ); foreach ( $categories as $category ) : ?>
		<div class="column half">
			<article class="highlights <?php echo $category->term_id; ?>" itemscope="" itemtype="https://schema.org/Article">
				<a href="<?php echo $category->slug; ?>" title="<?php echo $category->name; ?>" class="image-link">
					<img width="343" height="127" src="<?php echo z_taxonomy_image_url($category->term_id, 'thumbnail'); ?>" class="image wp-post-image no-display" alt="<?php echo $category->name; ?>" title="<?php echo $category->name; ?>" itemprop="image">
				</a>
				<div class="overlay">
					<span class="meta">
						<?php echo $category->description; ?>
					</span>
					<h2 itemprop="name"><a href="<?php echo $category->slug; ?>" title="<?php echo $category->name; ?>" itemprop="url"><?php echo $category->name; ?></a></h2>
				</div>
			</article>
		</div>
<?php endforeach; ?>

https://www.ads-software.com/plugins/categories-images/