google checkout is not applying any coupon codes

<?php

	function onAfterOrderConfirm(&$order,&$methods,$method_id) {
		$method =& $methods[$method_id];
		$currencyClass = hikashop::get('class.currency');
		$currencies = null;
		$currencies = $currencyClass->getCurrencies($order->order_currency_id,$currencies);
		$currency = $currencies[$order->order_currency_id];
		hikashop::loadUser(true,true); //reset user data in case the emails were changed in the email code
		$user = hikashop::loadUser(true);
		$lang = &JFactory::getLanguage();
		$locale = strtolower(substr($lang->get('tag'),0,2));
		$httpsHikashop = str_replace('http://','https://', HIKASHOP_LIVE);
		$notify_url = $httpsHikashop.'index.php?option=com_hikashop&ctrl=checkout&task=notify&notif_payment=googlecheckout&tmpl=component&lang='.$locale;
		$return_url = $httpsHikashop.'index.php?option=com_hikashop&ctrl=checkout&task=notify&notif_payment=googlecheckout&tmpl=component&user_return=1&lang='.$locale;
		$app =& JFactory::getApplication();
		$address = $app->getUserState( HIKASHOP_COMPONENT.'.billing_address');
		$price = round($order->cart->full_total->prices[0]->price_value_with_tax,(int)$currency->currency_locale['int_frac_digits']);
		$data = '<'.'?xml version="1.0" encoding="UTF-8"?'.'>'."\n";
$data .= '<checkout-shopping-cart xmlns="checkout.google.com/schema/2"><shopping-cart><items>';

foreach($order->cart->products as $product){

$data .= '<item><item-name>Order #'.$order->order_id.' - '.$product->order_product_name.'</item-name><item-description></item-description><unit-price currency="'.$currency->currency_code.'">'.$product->order_product_price.'</unit-price><quantity>'.$product->order_product_quantity.'</quantity></item>';

}
$data .= '<item><item-name>Order #'.$order->order_id.' - Shipping</item-name><item-description></item-description>
<unit-price currency="'.$currency->currency_code.'">'.$order->order_shipping_price.'</unit-price><quantity>1</quantity></item>';
$data .= '</items></shopping-cart><checkout-flow-support><merchant-checkout-flow-support/></checkout-flow-support></checkout-shopping-cart>';
		if( $method->payment_params->debug ) { echo 'XML Sent to Google<pre>'.htmlentities($data).'</pre>'; }
		if( $method->payment_params->server_to_server == true ) {
			$ret =& $this->webCall('checkout', $data, $method->payment_params);
			if( $ret !== false ) {
				if( preg_match('#<redirect-url>(.*)</redirect-url>#iU', $ret, $redirect) ) {
					$redirect = html_entity_decode(trim($redirect[1]));
					$app =& JFactory::getApplication();
					$app->redirect($redirect);
				}
				if( $method->payment_params->debug ) { echo 'Google call return<pre>'.htmlentities($ret).'</pre>'; }
			} 
			$url = '';
			$vars = '';
			$app =& JFactory::getApplication();
			$app->enqueueMessage('Google Checkout error. Please log-in to the backend of Google Checkout to see the log.');
		} else {
			$vars = array(
				'signature' => base64_encode($this->signature($data, $method->payment_params->merchant_key)),
				'cart' => base64_encode($data)
			);
			if( $method->payment_params->sandbox ) {
				$url = 'https://sandbox.google.com/checkout/api/checkout/v2/checkout/Merchant/';
			} else {
				$url = 'https://checkout.google.com/api/checkout/v2/checkout/Merchant/';
			}
			$url .= $method->payment_params->merchant_id;
		}
		JHTML::_('behavior.mootools');
		$app =& JFactory::getApplication();
		$name = $method->payment_type.'_end.php';
		$path = JPATH_THEMES.DS.$app->getTemplate().DS.'hikashoppayment'.DS.$name;
		if(!file_exists($path)){
			if(version_compare(JVERSION,'1.6','<')){
				$path = JPATH_PLUGINS .DS.'hikashoppayment'.DS.$name;
			}else{
				$path = JPATH_PLUGINS .DS.'hikashoppayment'.DS.$method->payment_type.DS.$name;
			}
			if(!file_exists($path)){
				return true;
			}
		}
		require($path);
		return true;
	}