Some of your trading partners have two levels of checks in place to validate the data you send them. The first level will verify that the data meets their EDI standards, and the second verifies that they can use the data you've sent them.
If you have recently sent a document to your trading partner that has failed this second level of verification, they will have sent you a kind of EDI document specifically to alert you to this error. Your trading partner might refer to this as an "864," and in WebForms, it shows up as an "Error Message."
We do our best to keep track of when you receive these kinds of documents and provide you with the necessary information to resolve the issue. You may, for example, receive an email explaining the error message and how to resolve it. You can also search for your error message here. If the one you have hasn't been posted yet, please feel free to ask about it in a new topic!