Add WordPress CPT to category and tag archives

add-cpt-to-category-and-tag-archives.php

<?php
/* ----------------------------------------------------------------------------
 * Add CPT to category and tag archives
 * ------------------------------------------------------------------------- */

function simple_add_custom_types( $query ) {
	if( is_category() || is_tag() && empty( $query->query_vars['suppress_filters'] ) ) {
		$post_types = get_post_types();
		$query->set( 'post_type', $post_type );
		return $query;
	}
}
add_filter( 'pre_get_posts', 'simple_add_custom_types');