Latest css for subtemplate not linking up to created page

I have this in my function.php

//load subtemplate level3andfour
function l3_style() {
	if( is_page_template('l3Sub.php') ) :
	wp_register_style('my-style', get_stylesheet_directory_uri() . '/css/subLevels.css', array(), '', 'all' );
	wp_enqueue_style( 'my-style' );
add_action('wp_enqueue_scripts', 'l3_style');

I have loaded the l3Sub.php subtemplate and assigned it to a page I created trough the wp-admin area.

this is the page btw:

but the css is not kicking in. Other css stylesheets i created works for other subtemplates but not this one. What am I missing?
thank you.