As Joe says, the small yellow wire on the "C" terminal must have battery voltage on it when the Master is turned on.
The black connector can be problematic as you can't easily tell if all the connections are being made adequately. Consider removing the individual wire spades from the black connector, cover them with shrink wrap and push them on to the regulator individually. You can then tell by feel if they are tight.
In this photo you can also see a dedicated ground wire back to the battery negative. And I used nut plates on the panel base so the regulator mounting screws could be removed without removing the top instrument cover and longer screws with standoffs. This makes the regulator relatively easy to change in the event (likely) that it goes TU some time in the future. Carry a spare.