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The buzzer with the black/white wire with red JST plug plugs into the two pins at the very front of the board (top of this picture).
It would seem you have no voltage sensing wire installed and that is why it reads "0" volts. You can see in my picture I have a single red wire plugged to the OUTSIDE pin where you have your buzzer incorrectly plugged into. That wire gores to the positive side of the battery loom. I just connected mine to the wire that connects to my XT60 battery connector. That wire tells the KK2.1 what the actual voltage of the battery is because the the KK2.1 is powered an ESC with only 5volts so it needs an direct way to find the battery voltage.
You will also notice I have no black(earth) wire installed and that pin has been broken off. That is because the KK2.1 is already earthed back to the battery so doesn't need it. The pin has been removed because if you accidently plug a two pin backwards on this you will blow up the KK2.1. Doing what I have done has no downside but prevents you from letting the smoke out.
Let me know if you are still confused.