Sometimes when you execute a map no output at all will be produced. This mainly happens when the input document is XML and most commonly caused by all of part of the input document of the map not being recognized. Here are some things to have a look at:
Use the Structure Editor - Switch over to the structure editor and have the sample document in question be the current document. Check that the highlighting is responding to the selected elements. You can also select an element and do right-click Show Sample to see if the element appears as desired. If the element does not appear, see the items below.
Does the Structure Match? - XML requires that the hierarchy of elements matches exactly what is defined in the structure. Start with the root element in the structure definition and check that the elements in your sample document correspond exactly.
Case Sensitivity - XML is case sensitive so make sure the case of the element matches that in shown in the map editor.
Namespace Issues - If the document uses XML namespaces, follow the namespace troubleshooting instructions.
Correct Visibility/Element Type/Group Type - Make sure these properties of each element are what you expect and match the actual document.
Emit Expressions - In some kinds of structures (like those found in FpML version 4.x) the root is a non-visible choice. If none of the members of the choice have an Emit expression that returns true, you will not get any output.