You can bump your post up to give it more visibility if no one has responded in a while. If no one needs what your selling when you post the thread it gets buried pretty quick. High prices will do the same thing, so make sure they are fair.
Try contacting them directly. Click on their username to start a conversation with them. More info here. http://mmb.maverick.to/threads/member-card.100504/
alot of times old posts get dug up by someone saying still available and the member hasnt been on in months or even longer the direct contact is the best way to try to reach them if they havent responded to the post good luck