Can't get my WP_Query loop to work, cannot figure out why `category__in` won't work. Just want to pull certain categories FROM my custom post type

    
    $args = array(
      'post_type' => 'bbt',
      'category__in' => array(90,89)
    );
    
    $loop = new WP_Query($args);


when I use `echo $loop->found_posts;` it does returns 0, BUT I have 2 posts in total from those categories


EDIT: 
Here is how the category was assigned:

    	$labels = array(
	    'name' => _x( 'Big Boys Toys Categories', 'taxonomy general name' ),
	    'singular_name' => _x( 'Tag', 'taxonomy singular name' ),
	    'search_items' =>  __( 'Search Types' ),
	    'all_items' => __( 'All Tags' ),
	    'parent_item' => __( 'Parent Tag' ),
	    'parent_item_colon' => __( 'Parent Tag:' ),
	    'edit_item' => __( 'Edit Tags' ),
	    'update_item' => __( 'Update Tag' ),
	    'add_new_item' => __( 'Add New Tag' ),
	    'new_item_name' => __( 'New Tag Name' ),
	);

	// Register Custom Taxonomy
	register_taxonomy('tagbbt',array('bbt'), array(
	    'hierarchical' => true, // define whether to use a system like tags or categories
	    'labels' => $labels,
	    'show_ui' => true,
	    'query_var' => true,
	    'rewrite' => array( 'slug' => 'tag-bbt' ),
	));