2 things come to mind. Fuses and earth wire. Check all the fuses specially the big ones. If they're ok, disconnect the battery overnight and try again in the morning. Secondly, connect a wire from the negative of the battery to the chassis and another to the engine. Then try the electrics. There is also a fuel cut off switch in the cockpit somewhere, not sure where it is. Google for it. That cuts off the fuel in case of an accident. This will prevent your car from starting but not prevent the electics from working. You just have to check the fuses specially the big ones and the earth wire