The small white fly lead is used to convert from our screw on style connectors on the CATV (coax style) cable to the push on style fitting on the V6 so you do need it. If the cable you are trying to plug in to the box has a push on type connector like a normal tv aerial coax its likely this is not the correct cable. You can try loading the V6 in the same location as the 1st box using its cable that you know is right and has signal if it loads then this other cable is either incorrect or not connected back to the main cable at your properties entry point.
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