problem showing subItem items on menu

Hi to all,
I using a child Theme from this:

but I have some problem to show subItem items on menu.
I found that if I edit this (code found in header.php):

$navbar .= wp_nav_menu(
		array(
		'menu_id' => 'nav',
		'theme_location' 	=> 'primary',
		'container' 		=> false, //<nav> or <div> class
		'menu_class' 		=> 'offcanvas-links', //<ul> class
		'fallback_cb' 		=> 'wp_page_menu',
		'depth'				=> 0,
		'echo'				=> false,
		'sub_menu' => true
		)
	);

changing this

depth’=> 0,

with 0 instead the original 1, the menu show me all the element but without the appropriate indentation. How can I solve it?

so why

0 (default) Displays pages at any depth and arranges them hierarchically in nested lists

don’t give me any nested lists?