Risolto, avevo messo qualche parametro importante come 'show_ui', 'show_in_menu'.
codice:
function create_post_type_excursion() {
$args = array(
'labels' => array(
'name' => __( 'Escursioni', 'qns' ),
'singular_name' => __( 'Escursioni', 'qns' ),
'add_new' => __('Aggiungi nuovo', 'qns' ),
'add_new_item' => __('Aggiungi nuova escursione' , 'qns' )
),
'public' => true,
'publicly_queryable' => true,
'show_ui' => true,
'show_in_menu' => true,
'menu_position' => 5,
'menu_icon' => 'dashicons-location',
'query_var' => true,
'rewrite' => array( 'slug' => 'book' ),
'capability_type' => 'post',
'has_archive' => true,
'hierarchical' => false,
'supports' => array( 'title', 'editor', 'author', 'thumbnail', 'excerpt', 'comments' )
);
register_post_type('excursion', $args);
}
add_action( 'init', 'create_post_type_excursion' );
Grazie!