In DJI Fly, go to ABOUT with the drone paired & powered up. No need to spin the props. Find the Flight Controller Serial Number among the three or so, this is the one you want. If I recall, all Os are actually zeros.I'm trying to register my M4P but the FAA isn't recognizing the serial number. On my dji account it has the serial number there but says I haven't flown it at all, but I've put in maybe 10 hours on it.. any thoughts in diagnosing this?