I have a hierarchical custom post type, but the Parent field is missing in the block editor sidebar.

register_post_type( 'guides',
    [
        'public' => true,
        'hierarchical' => true,
        'has_archive' => true,
        'menu_position' => 20,
        'menu_icon' => 'dashicons-format-aside',
        'rewrite' => [
            'slug' => 'guides',
            'with_front' => false,
            'feeds' => true
        ],
        'supports' => [ 'title', 'editor', 'excerpt', 'revisions', 'page-attributes' ],
        'show_in_rest' => true,
        'rest_base' => 'cs_guides',
        'taxonomies' => [ 'topic', 'county' ],
        'labels' => [
            'name' => __( 'Guides', 'textdomain' ),
            'singular_name' => __( 'Guide', 'textdomain' ),
            'add_new' => __( 'Add New', 'textdomain' ),
            'add_new_item' => __( 'Add New Guide', 'textdomain' ),
            'edit_item' => __( 'Edit Guide', 'textdomain' ),
            'new_item' => __( 'New Guide', 'textdomain' ),
            'all_items' => __( 'All Guides', 'textdomain' ),
            'view_item' => __( 'View Guide', 'textdomain' ),
            'search_items' => __( 'Search Guides', 'textdomain' ),
            'not_found' =>  __( 'No Guides found', 'textdomain' ),
            'not_found_in_trash' => __( 'No Guides found in trash', 'textdomain' ),
            'parent_item_colon' => '',
            'menu_name' => __( 'Guides', 'textdomain' ),
        ]
    ]
);