add submenu page is not working

I have following code which is not working ie not adding any submenu in plugin:

function acp_add_pages() {
    $dirs = array('acpcf'=>'C F','acpcj'=>'C J','acppj'=>'P N');
    add_menu_page('Welcome To my plugin', 'menu','manage_options','acp_toplevel', 'acp_gen','dashicons-tickets');
    add_submenu_page('acp_toplevel','General Options','General Options','manage_options','acp_toplevel','acp_gen');
    foreach($dirs as $dir=>$submenu){
         if(is_dir($dir)){
             add_submenu_page('acp_toplevel',$submenu.' Settings',$submenu,'manage_options',$dir.'/'.$dir.'.php');
        }
    }
}
add_action('admin_menu', 'acp_add_pages');
function acp_gen(){
    ?>
<div class="wrap">
<h2>Welcome To general option</h2>
</div>
<?php
}

The directories and files are there and is_dir returns true so What I am missing here ?

Thanks