WP自定义帖子类型分类-需要创建类别

我正在尝试创建一个名为" incentive "的自定义帖子类型。在这个自定义帖子类型中，我想创建一个名为"照明激励"的类别。我创建了一个函数来注册自定义帖子类型和创建分类法/类别。但是，由于某种原因，我无法注册分类法/类别。分类法/类别不会出现在WP仪表板中。此外，"激励"与"照明激励"的层次结构似乎有点混淆。这是我的代码

add_action('init', 'incentive_register');
function incentive_register() {
    $labels = array(
        'name' => _x('Lighting Incentives', 'post type general name'),
        'singular_name' => _x('Lighting Incentive', 'post type singular name'),
        'add_new' => _x('Add New', 'Lighting Incentive'),
        'add_new_item' => __('Add New Lighting Incentive'),
        'edit_item' => __('Edit Lighting Incentive'),
        'new_item' => __('New Lighting Incentive'),
        'view_item' => __('View Incentive'),
        'search_items' => __('Search Incentives'),
        'not_found' =>  __('Nothing found'),
        'not_found_in_trash' => __('Nothing found in Trash'),
        'parent_item_colon' => ''
    );
    $args = array(
        'labels' => $labels,
        'public' => true,
        'publicly_queryable' => true,
        'show_ui' => true,
        'query_var' => true,
        'menu_icon' => get_stylesheet_directory_uri() . '/article16.png',
        'rewrite' => true,
        'capability_type' => 'post',
        'has_archive' => 'lighting-incentives',
        'menu_position' => null,
        'parent_item' => 'Incentives',
        'supports' => array('title','editor','thumbnail','excerpt','custom-fields','post-formats')
      ); 
    register_post_type( 'Incentive' , $args );
    register_taxonomy_for_object_type('category','Incentive');
        flush_rewrite_rules();
}