Custom Post Types and Registering Tags

I am currently using a theme which has a Custom Post Type set up (portfolio posts) but the Tag function is not registering. I have tried some of the suggested techniques but all break the code.

Currently:

//Let's create out Custom post Types & taxonomies
	add_action('init', 'timelessCustomPortfolioType');
	add_action('init', 'timelessPortfolioCustomTaxonomy');

	function timelessCustomPortfolioType() {

		register_post_type( 'portfolio_posts',
			array(
				'labels' => array(
					'name' => __( 'Portfolio Posts' ),
					'singular_name' => __( 'Portfolio Post' )
				),

				'public' => true,
				'menu_position' => 8,
				'query_var' => true,
				'supports' => array(

					'title',
					'editor',
					'custom-fields',
					'comments',
					'excerpt'

				),

				'rewrite' => array(

					'slug' => ddp('portfolio_slug'),
					'with_front' => false

				)
			)
		);

	}

	//ADDS OUR PORTFOLIO CATEGORIES
	function timelessPortfolioCustomTaxonomy() {

		//Portfolio Categories
		register_taxonomy(

			'portfolio_cats',
			'portfolio_posts',
			array(

				'hierarchical' => true,
				'label' => 'Portfolio Categories'

			)

		);

	}

Any thoughts would be greatly appreciated.