我没有在amzon mws api-GetProductCategoriesForSKU中得到正确的结果

Question

I'm using AmazonMwsComplete-master -> AmazonPhpClientLibrary -> MarketplaceWebServiceProducts. I haven't get result when I use GetProductCategoriesForSKU sample. I have given all credential in .config.inc.php. Following is the code I used:

require_once('.config.inc.php');

$serviceUrl = "https://mws.amazonservices.in/Products/2011-10-01";
$config = array (
    'ServiceURL' => $serviceUrl,
    'ProxyHost' => null,
    'ProxyPort' => -1,
    'ProxyUsername' => null,
    'ProxyPassword' => null,
    'MaxErrorRetry' => 3,
);

$service = new MarketplaceWebServiceProducts_Client(
    AWS_ACCESS_KEY_ID,
    AWS_SECRET_ACCESS_KEY,
    APPLICATION_NAME,
    APPLICATION_VERSION,
    $config);
$service = new MarketplaceWebServiceProducts_Mock();

$request = new MarketplaceWebServiceProducts_Model_GetProductCategoriesForSKURequest();
$request->setSellerId('A2VE4N396R31ZE');
$request->setSellerSKU('552812PMWAAA223IH000003');

invokeGetProductCategoriesForSKU($service, $request);

I get the following error:

No category name found in response, Service Response ==================================‌​=========
String String String String String ResponseHeaderMetadata