Custom register_taxonomy ins’t showing custom Nav menu

The only thing that I see is the argument 'query_var'=>true, it can be set to false, but the default value is the taxonomy name, so set it to true is maybe the cause of the failure, even the codex example set it to true, I think it can be great to try

 register_taxonomy(
      'works_category', 
      'works', 
           array(
                'hierarchical' => true, 
                'label' => 'Works Category', 
                'query_var' => 'works_category', 
                'rewrite' => array('slug' => 'works-categorys')
           )
 );

Or just suppress query_var from the array ?