我需要使用C#通过亚马逊MWS API更新亚马逊市场中的MerchantOrderID。
所以，首先我创建XML文件如下：

<?xml version="1.0"?>
<AmazonEnvelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="amzn-envelope.xsd">
  <Header>
    <DocumentVersion>1.01</DocumentVersion>
    <MerchantIdentifier>M_STORE_3918753</MerchantIdentifier>
  </Header>
  <MessageType>OrderAcknowledgement</MessageType>
  <Message>
    <MessageID>1</MessageID>
    <OrderAcknowledgement>
      <AmazonOrderID>104-9209939-0469021</AmazonOrderID>
      <MerchantOrderID>100828163</MerchantOrderID>
      <StatusCode>Success</StatusCode>
      <Item>
        <AmazonOrderItemCode>11111111111111</AmazonOrderItemCode>
        <MerchantOrderItemID>111111</MerchantOrderItemID>
        <AmazonOrderItemCode>22222222222222</AmazonOrderItemCode>
        <MerchantOrderItemID>222222222</MerchantOrderItemID>
      </Item>
    </OrderAcknowledgement>
  </Message>
</AmazonEnvelope>

然后我尝试调用Amazon MWS SubmitFeed：

SubmitFeedRequest request = new SubmitFeedRequest();
        request.Merchant = merchantId;
        request.MarketplaceIdList = new IdList();
        request.MarketplaceIdList.Id = new List<string>(new string[] { marketplaceId });

        request.FeedContent = File.Open(path, FileMode.Open, FileAccess.Read);

        request.ContentMD5 = MarketplaceWebServiceClient.CalculateContentMD5(request.FeedContent);
        request.FeedContent.Position = 0;

        request.FeedType = "_POST_ORDER_ACKNOWLEDGEMENT_DATA_";

        MarketplaceWebService.MarketplaceWebService serviceFeed = new MarketplaceWebServiceClient(
                accessKeyId,
                secretAccessKey,
                applicationName,
                applicationVersion,
                configFeed);

        SubmitFeedResponse response = serviceFeed.SubmitFeed(request);

它成功提交，但当我在Amazon（www.example.com）中打开订单sellercentral.amazon.com时，它显示“未保存”：您的商家订单编号：#未保存
谁能帮助我，什么是错的或我应该做什么？
谢谢！