Image Size

Currently pulling a list of subcategories with images, and it does not seem to reflect my choice of image size (thumbnail), rather displays the full-size image.

Code I am using:

<?php
	$id = get_query_var('cat');
	$args = array(	'parent' => $id );
	foreach (get_categories($args) as $cat) : ?>

	<div class="item">
		<a href="<?php echo get_category_link($cat->term_id); ?>"><img src="<?php echo z_taxonomy_image_url($cat->term_id, 'thumbnail'); ?>" />
		<span class="title"><?php echo $cat->cat_name; ?></span></a>
	</div>

	<?php endforeach; ?>

I’ve also tried using the ‘NULL, array(100, 100)’ instead of the ‘thumbnail’ image size and all the images show up broken/blank.

Please advise.

https://wordpress.org/plugins/categories-images/