Content API for Shopping not working in OpenCart - opencart2.x

Question

I am trying to integrate the Content API for Shopping in OpenCart into my PHP app and getting this error:
Fatal error: Uncaught exception 'GSC_ParseError' with message 'Not
Found' in
/home/public_html/admin/controller/module/GShoppingContent.php:2805
Stack trace: #0
/home/public_html/admin/controller/module/GShoppingContent.php(980):
_GSC_AtomParser::parse('Not Found') #1 /home/public_html/admin/controller/module/contentapi.php(76):
GSC_Client->insertProduct(Object(GSC_Product)) #2 [internal function]:
ControllerModuleContentApi->index(Array) #3
/home//public_html/vqmod/vqcache/vq2-system_modification_system_engine_action.php(71):
call_user_func(Array, Array) #4
/home//public_html/vqmod/vqcache/vq2-system_engine_front.php(89):
Action->execute(Object(Registry)) #5
/home//public_html/vqmod/vqcache/vq2-system_engine_front.php(63):
Front->execute(Object(Action)) #6
/home//public_html/admin/index.php(175):
Front->dispatch(Object(Action), Object(Action)) #7 {main} thrown in
/home//public_html/admin/controller/module/GShoppingContent.php on
line 2805
Here's my code:
require_once('GShoppingContent.php');
class ControllerModuleContentApi extends Controller {
private $error = array();
public function index() {
$this->load->language('module/contentapi');
$this->db->query("
CREATE TABLE IF NOT EXISTS `contentapi` (
`contentapiid` int(11) NOT NULL AUTO_INCREMENT,
`contentapimerchantid` varchar(256) NOT NULL,
`contentapiemail` varchar(256) NOT NULL,
`contentapipassword` varchar(256) NOT NULL,
PRIMARY KEY (`contentapiid`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
");
$contentAPI11=$this->db->query("select * from contentapi");
$data['contentapidata'] = $contentAPI11->rows;
if (isset($this->request->post['merchantid']) && isset($this->request->post['GoogleMerchantEmail']) && isset($this->request->post['GoogleMerchantPassword'] )) {
$merchantid=$this->request->post['merchantid'];
$GoogleMerchantEmail=$this->request->post['GoogleMerchantEmail'];
$GoogleMerchantPassword=$this->request->post['GoogleMerchantPassword'];
$primaryid=$this->request->post['primaryid'];
$this->db->query("UPDATE contentapi SET contentapimerchantid='$merchantid',contentapiemail='$GoogleMerchantEmail',contentapipassword='$GoogleMerchantPassword' where contentapiid='$primaryid'");
}
$retrieveapidetails=$this->db->query("select * from contentapi");
if($retrieveapidetails->num_rows>0)
{
$retrieveapidetails1=$retrieveapidetails->rows;
foreach($retrieveapidetails1 as $retrieveapidetails2)
{
$contentapimerchantid=$retrieveapidetails2["contentapimerchantid"];
$contentapiemail=$retrieveapidetails2["contentapiemail"];
$contentapipassword=$retrieveapidetails2["contentapipassword"];
}
$retrieveproducts=$this->db->query("select oc_product.model,oc_product.sku,oc_product.price,oc_product.image,oc_product_description.name,oc_product_description.description from oc_product,oc_product_description where oc_product.product_id=oc_product_description.product_id");
$retrieveproducts1=$retrieveproducts->rows;
$client = new GSC_Client($contentapimerchantid);
$client->login($contentapiemail, $contentapipassword);
foreach($retrieveproducts1 as $retrieveproducts2)
{
$productid=$retrieveproducts2["product_id"];
$productname=$retrieveproducts2["name"];
$productmodel=$retrieveproducts2["model"];
$productprice=$retrieveproducts2["price"];
$productimage=$retrieveproducts2["image"];
$productsku=$retrieveproducts2["sku"];
$productdescription=$retrieveproducts2["description"];
$product = new GSC_Product();
$product->setTitle($productname);
$product->setDescription($productdescription);
$link = 'https://testingsite.com/index.php?route=product/product&product_id=' . $productid;
$product->setProductLink($link);
$product->setSKU($productsku);
$product->setImageLink('https://testingsite.com/'.$productimage);
$product->setBrand($productimage);
$product->setPrice($productprice, 'usd');
$entry = $client->insertProduct($product);
}
}