Got "The page you are trying to access is not valid." When try to access the document

We have a EchoSign document already sent to Adobe cloud via v20 API, after sent successfully I get the URL for accessing the document. And in our application which is a cluster having two app servers, say Server A and Server B and we send document to Adobe via Server A. At this time, when you try to open the document URL from Server A, it is fine; but when you try to open the URL from Server B, it reports "The page you are trying to access is not valid.". Any idea about this? For both Server A and Server B, the URL is the same, don't why this happens.