Simon it looks like you have a single quotes around the value of 'FileStartWith' attribute. If you look at the attributes of the flow files that were routed to the 'unmatched' relationship I think you'd see values of something like "'INCOMING.D'170322" not "INCOMING.D170322". If you remove the quotes I think it should work as expected. Also, your attribute for date doesn't seem to be valid EL. It looks like you are missing a closing bracket.