Same happened to me with two different A3s. Did you solve the problem?
That's just a dead board plain and simple. Aside from getting warranty work done on it there's not a lot you can do. Could be power circuity, and if your good with soldering iron you might be able to fix it. But i would not advise doing it while under warranty. I'd just get it replaced. Unfortunately profitability is going to be much less by the time you'd get it back. Personally i'd ride it out on two boards till the gold rush is over, then send it in.
Unplug and replug the white control cables. CHeck them to see that the wire is actually done properly, IE the crimp to the metal pin on the inside of the plug, you can check with a multimeter. I had an issue with an Improperly seated connector on an S9. replugging fixed that same problem. If the board was dead, or the asics you would at least have PCB temps on the screen for it. This means no data/control from the board.
