Yamaha sent and had the technician replace 2 boards in that key drive box but that did not resolve the problem. All the cables, connection pins, etc. were also checked, actually several times. Yamaha is sending 3 more boards for replacement. I was told by my dealer, and essentially confirmed by Martin at Yamaha, that if that does not fix the problem, the piano will be replaced. Considering that it is a brand new piano and I only had it 3 days before it stopped working, this seems like the reasonable thing to do, as the technician cannot bench test all the boards and wiring on his back under the piano. If replacing boards does not fix the problem, it needs to go back to Yamaha.
We will see what happens in the next few days as the new boards were overnighted to the technician.