PX4 doesn't power up successfully

#1

I just bought a PX4. (Pixhawk 2.1 - px4v3)
When I power up my PX4 it goes through the orange LED’s and e few tones and then finishes with a tone like “bah bom” and LED’s off. No green.
I try plugging in to Mission Planner and it’s detected OK.
I try a firmware update using Arduplane v3.9.8. MP asks if it’s a “CubeBlack” (I assume it is because it has the black Cube on its back.) The flash appears to work ok but same issue “bah bom” tone and no green LED’s
Any ideas or help greatly appreciated as I am a total nube.

#2

Best to ask about ArduPilot at discuss.ardupilot.org