Triggers or colliders and bools seems like the way to go. You need to provide some information what exactly doesn’t work.
As I see it, you need three elements for a simple prototype, like three cubes. Use a clean scene, and worry about the looks later. You need to add colliders and then use either On Collision or On Trigger global events, to detect whether they collide or touch. You can also use a state with appropriate actions that listen. You need to make sure to use the correct versions. When you tick the trigger checkbox on the colliders, you need to use trigger actions. You also need to use the correct pair, there’s a default set for 3d, and another one for 2D. Can you make triggers or colliders work?
You want to use the On Trigger/Collider Enter and On Trigger/Collider Stay. I’d use the global system events. I.e. when they collide, or are still intersecting, the state is active,
Next, you could use a bool or tags to indicate whether that cube has power. When you collide, check wether the connecting cube has power, and if so, also set power to true, if not, set to false. Only the conductor box always has power.
Break down your process and pinpoint what exactly doesn’t work.