I'm no airplane expert, but it looked like none of the landing gear came out. If only one of the three trucks failed to deploy I would suspect a mechanical problem; but all three I would think would have to be a computer or electrical issue. Perhaps part of the training is if one truck fails to deploy they retract all and land like that? It will be interesting to see what the final determination is.

We have to give credit to the pilot. That was a beautifully executed emergency landing!