Menu links with sub-menu's not working

Weird problem here. I have a drop-down menu on my site and all the links work great except the ones that have a sub-menu attached. I have the following in functions.php and doing all the editing through ‘Appearance/Menus’ :

<?php
function register_my_menus() {
register_nav_menus(
array( ‘header-menu’ => __( ‘Header Menu’ ) )
);
}
add_action( ‘init’, ‘register_my_menus’ );
?>

Website is at:
https://luxetransportationsd.com/

Any idea what’s going on?