Displaying WordPress posts from post and custom post type in custom taxonomy

If you’d like to include the post post type, it needs to be added to the post_type parameter for WP_Query:

        $args = array('post_type' => array( 'post', 'resources' ),
            'tax_query' => array(
                array(
                    'taxonomy' => 'resource',
                    'field' => 'slug',
                    'terms' => $custom_term->slug,
                ),
            ),
         );