عدم نمایش منو سمت راست

<?php
/*
Plugin Name: wordpress api
Plugin URI: http://wp-persian.com/wp-jalali
Description: Full Jalali calendar support for Wordpress and localization improvements for Persian/Afghan/Tajik users.
Version: 5.0.1
Author: Mehdi
Author URI: http://zakrot.com/
Text Domain: ztjalali
Domain Path: /languages
*/
define('WP_API_DIR',plugin_dir_path(__FILE__));
define('WP_API_URL',plugin_dir_url(__FILE__));
define('WP_API_INC',WP_API_DIR.'/inc/');

register_activation_hook(__FILE__,'wp_api_plugin_activation');
register_deactivation_hook(__FILE__,'wp_api_plugin_deactivation');

function wp_api_plugin_activation(){

};

function wp_api_plugin_deactivation(){

};

if(is_admin()){
    include WP_API_INC.'admin/menu2.php';
};









<?php
add_action('admin_menu','wp_api_fun');

function wp_api_fun()
{
    add_menu_page(
                'تنظیمات',
                'تنظیمات پلاگین',
                'manage_option',
                'wp_api',
                'wp_api_register'
    );
}

function wp_api_register(){

    echo '<h1>hello</h1>';

}