Javascript not included

You’re mixing up the singular wp_enqueue_script, which adds a script, with the plural wp_enqueue_scripts which is an action and a function that triggers that action. I think you want

function theme_scripts()
{
    wp_enqueue_script( 'custom-script', get_template_directory_uri() . '/js/menu-fix.js', array('jquery'), '1.0', true);
}
add_action('wp_enqueue_scripts', 'theme_scripts');

i.e. register against the enqueue_scripts-plural action that calls enqueue_script-singular.