Hi Tim
    Another thing to try after Steve's a advice is to go into test mode and enter the GI test. There are several GI strings on each wpc game just check if at least some globes light up on each string.    If not check the 5 fuses On the lower left corner of your driver board.

In addition to what Daniel has suggested, also just follow the 'chain' for that string.  Have you tested voltages at the sockets?  It may be something simple like further up the chain a wire has popped off disconnecting the slings...