Customiser sections not being displayed with `active_callback`

The is_single template tag takes an optional parameter and therefore does not work for an active callback. Try this instead:

function callback_single() { return is_single(); }

$wp_customize->add_section('section_template_single' , array(
    'title'             => __('Single Links', $this->text_domain),
    'priority'          => 10,
    'panel'             => 'panel_templates',
    'active_callback'   => 'callback_single'
));

You also have “wp_customise” instead of “wp_customize.”

Source: http://ottopress.com/2015/whats-new-with-the-customizer/