Why does my Castle settlement show insufficient power?

There are a bunch of lightbulbs and an industrial water purifier that need power.

You can see the purifier out of one of the windows. There is a pylon with a switch on it in the courtyard you can connect to to hook up all the light bulbs and the purifier. It was not obvious to me until I traced the wires from the lights.

Since there's a switch on the pylon, you might need to make sure that it is actually switched on.

In case anyone still has problems with the lights at the castle, it is right in our faces. I feel stupid after realizing what needed to be done. By the workbench there should be a power switch. You need to hook up a generator into that switch. I was also focused on the big thing in the middle and didn't pay attention.