All fees paid are non-refundable.
A visa does not guarantee entry into the U.S.
A visa allows a foreign citizen coming from abroad, to travel to the United States port-of-entry and request permission to enter the U.S.
Permission to enter can only be given by a Department of Homeland Security (DHS), Customs and Border Protection (CBP) official.
You may not enter the U.S. with an expired visa. The visa must be valid at the time you enter the U.S.