mrpsihopath

Well, I found what was wrong: the plugin doesn’t register neither tags, nor categories. If anyone will run into the same problem, here’s code to solve it.

register_taxonomy(
		'news_category', 'news', array(
			'show_ui' => true,
			'show_admin_column' => true,
			'show_in_nav_menus' => true,
			'show_tagcloud' => false,
			'hierarchical' => true,
			'rewrite' => array('slug' => 'news_category','with_front' => false)
		)
	);
register_taxonomy(
		'news_post_tag', 'news', array(
			'hierarchical' => false,
			'public' => true,
			'show_ui' => true,
			'show_admin_column' => true,
			'show_in_nav_menus' => true,
			'show_tagcloud' => true,
			'rewrite' => array('slug' => 'news_post_tag','with_front' => false)
	));

I added it in the news_cpt_init() function, after
register_post_type('new',$args);