Filter custom content by parent category and subcategory

I found this bit of code here that shows (supposed to) the posts in the child category. I took out a bunch of stuff I don’t need (I think).

I get the heading of taxonomy I’m viewing but none of my custom posts are loading. Can anybody help please? No posts loaded before I removed anything from the original code so I don’t think I broke anything>

<div class="overflow-container">
  <?php
  $term = get_queried_object();
  $tax = 'department';
  $parents = $term->parent;
  $term_id = $term->term_id;

     if ($parents > 0 && is_tax($tax, $tax->name)){

        $args = array(
         'post_type' => 'project_post',
         'posts_per_page' => -1,
         $tax => $term->name,
        );
        echo "<h2>".$term->name."</h2>";

 $wp_query = new WP_Query($args);
 if( $wp_query->have_posts() ):
 while ( $wp_query->have_posts() ) : $wp_query->the_post();
?>

 <article <?php $k = $style_index % $styles_count; echo "class=$style_classes[$k]"; $style_index++; ?>>
  <div id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
      <div class="entry-content">
	<div class="thumbnail">
									        <!-- get featured image -->
									<?php
 $mobile = wp_get_attachment_image_src( get_post_thumbnail_id(), 'thumbnail' );
 $tablet = wp_get_attachment_image_src( get_post_thumbnail_id(), 'medium' ) ;
 $desktop = wp_get_attachment_image_src( get_post_thumbnail_id(), 'large' ) ;
?>
									<img data-interchange="[<?php echo $mobile[0]; ?>, (small)], [<?php echo $tablet[0]; ?>, (medium)], [<?php echo $desktop[0]; ?>, (large)]">
								</div>
 <div class="excerpt">
  <header>
     <h2><?php the_title(); ?></h2>
  </header>
									  <?php the_excerpt(); ?>
 </div>
</div>
<a href="<?php the_permalink(); ?>" class="entry-overlay"></a>
</div>
</article>

 <?php
    endwhile;
    endif;
    wp_reset_postdata();
 }
?>