title: "one or more items are invalid" in Amazon MWS XML Feed
body: <p>This is similar to this question, however the answer does not seem to work in my situation: <a href="https://stackoverflow.com/questions/16859841/amazon-mws-feed-api-issue-in-updating-order-status">Amazon MWS Feed API Issue in updating Order status</a></p>
  
  <p>I am submitting the following XML:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;AmazonEnvelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="amzn-envelope.xsd"&gt;
  &lt;Header&gt;
      &lt;DocumentVersion&gt;1.01&lt;/DocumentVersion&gt;
      &lt;MerchantIdentifier&gt;1234567&lt;/MerchantIdentifier&gt;
  &lt;/Header&gt;
  &lt;MessageType&gt;OrderFulfillment&lt;/MessageType&gt;
  &lt;Message&gt;
      &lt;MessageID&gt;1&lt;/MessageID&gt;
      &lt;OrderFulfillment&gt;
          &lt;AmazonOrderID&gt;000-1111111-2222222&lt;/AmazonOrderID&gt;
          &lt;MerchantFullfillmentID&gt;1234567&lt;/MerchantFullfillmentID&gt;
          &lt;FulfillmentDate&gt;2016-04-27T16:13:46-05:00&lt;/FulfillmentDate&gt;
          &lt;FulfillmentData&gt;
              &lt;CarrierName&gt;UPS&lt;/CarrierName&gt;
              &lt;ShippingMethod&gt;UPS Ground&lt;/ShippingMethod&gt;
              &lt;ShipperTrackingNumber&gt;1234567&lt;/ShipperTrackingNumber&gt;
          &lt;/FulfillmentData&gt;
          &lt;Item&gt;
              &lt;MerchantOrderItemID&gt;SKU&lt;/MerchantOrderItemID&gt;
              &lt;MerchantFulfillmentItemID&gt;SKU&lt;/MerchantFulfillmentItemID&gt;
              &lt;Quantity&gt;1&lt;/Quantity&gt;
          &lt;/Item&gt;
      &lt;/OrderFulfillment&gt;
  &lt;/Message&gt;
  &lt;/AmazonEnvelope&gt;
  </code></pre>
  
  <p>I am receiving this message when I check the feed status:</p>
  
  <pre><code>&lt;Result&gt;
      &lt;MessageID&gt;1&lt;/MessageID&gt;
      &lt;ResultCode&gt;Error&lt;/ResultCode&gt;
      &lt;ResultMessageCode&gt;25&lt;/ResultMessageCode&gt;
      &lt;ResultDescription&gt;We are unable to process the XML feed because one or more items are invalid. Please re-submit the feed.&lt;/ResultDescription&gt;
  &lt;/Result&gt;
  </code></pre>
  
  <p>Are there any clear errors in this document?</p>