I have a new Holybro Pixhawk 1. I flew it on a quadcopter yesterday, and it seemed to fly fine. I took it home and put it on Mission Planner with USB to change the flight modes, but only the little green FMU PWR LED would come on. I disconnected the USB cable and put it on a battery. The ESCs beeped, but only the FMU PWR LED came on again. What does this mean?