I am using IDE 1.6.9....... And after updating Arduino AVR Boards to v. 1.6.12, I can no longer upload to board.Going back to v. 1.6.11 and it works again. Tried this on Arduino Mega2560 and Nano. Same result. Any idea?
If no one here can answer that. I'd bet the good folks on the Arduino forum would know. https://forum.arduino.cc