Check Upper Battery Connections
If the Lid is not clicked down properly or any of the connections are loose the lights may not work. Open the Lid and Bend the Metal Battery Connectors downward so they make better connections. (Both Ends for you to bend downward are indicated with Arrows)
Check Lower Battery Connections
Remove the two batteries from the compartment and make sure the metal tabs below the batteries are bent up enough to make a solid connection. In the picture the metal tab on the left is too low and needs to be bent upwards to make a good connection.
Check that Case Lid Closes Flat and Secure
The Lid can become bent or can easily not close fully. If your Lid is bent like in the picture; open the lid, bend it backwards to straighten it out, and then when it closes it should close flush. Also make sure that it clicks shut and both tabs secure themselves to the lower case.