Try adding this to your theme’s function.php. It worked for me, hope it helps.
// PRETTY PHOTO //
add_action( 'wp_enqueue_scripts', 'lightbox' );
function lightbox() {
global $woocommerce;
$suffix = defined( 'SCRIPT_DEBUG' ) && SCRIPT_DEBUG ? '' : '.min';
{
wp_enqueue_script( 'prettyPhoto', $woocommerce->plugin_url() . '/assets/js/prettyPhoto/jquery.prettyPhoto' . $suffix . '.js', array( 'jquery' ), $woocommerce->version, true );
wp_enqueue_script( 'prettyPhoto-init', $woocommerce->plugin_url() . '/assets/js/prettyPhoto/jquery.prettyPhoto.init' . $suffix . '.js', array( 'jquery' ), $woocommerce->version, true );
wp_enqueue_style( 'woocommerce_prettyPhoto_css', $woocommerce->plugin_url() . '/assets/css/prettyPhoto.css' );
}
}