A latching disconnect only needs power to switch it on or off. Once it is on or off it just sits there waiting for the next event.
The solenoid should have two big terminals and two small ones. The two small ones are going to be power and ground. The two big ones are going to be coming from the battery and then to the house. I bet if you check for voltage at the big terminals, the battery one will have 12v, and the other one will not.
The power side of the small terminals should go to the switch. Or maybe to a little CPU, I don't know. And, there may be fuses at the solenoid. I'm rambling, but the basic theory is, you press the switch and it sends a momentary power to the solenoid. That's all it takes to throw the "latch" from off to on. Once it's on, the solenoid stays on, it does not need to be powered.
So if you have 12v on the battery side of the solenoid and nothing on the house side, your job is to figure out if the small power terminals get 12v (or -12v) when you press the switch. If it does, the solenoid is not working. If it doesn't get any juice there, then you have a problem with the switch or the supply to the switch or maybe a CPU that is part of the system. And, there will be fuses in that control circuitry somewhere.
If you need more clarification, please ask.