Assume if i have Xpath Expression to extract certain value
Pre Requisite : create a Variable name Var with value=abc
//ASObject/CreateObject[contains(text(),'${Var}')] - does not fetch any value from response
//ASObject/CreateObject[contains(text(),'abc')] - works fine and able to extract a value from response.
In the Variable extractor panel, your variable ${Var} is not processed i.e not replaced by its value. That's why you won't see the result right away in that configuration panel.
But if you run a user validation, your variable should be replaced and then your XPath should work.
Have you tried?