Every case is unique, but here’s what happened to me.
My goal was to receive a CSV file, and have it split into multiple output files in the Send Port. I did specify my CSV flat-file pipeline in my Receive Location’s Pipeline.
I took over a project at a new client. And while re-writing the code, I changed the names of all the programs and namespaces from XYZLongCompany, to just XYZ.
When I built the receive location on the test system, I copied the old long names, instead of the new short names into my Receive Location Pipeline properties, where you specify the “Document Spec Name” and the “Header Spec Name”.
This MSDN post shows how to find the document spec name by expanding the schemas then showing the properties. I can’t include any screen shots with actual client name.