Arduino Nano not responding with yellow led blinking fast
I successfully restored both boards using the reset button:
- Power off the board (I disconnected the USB cable from computer)
- Press and hold the reset button
- Connect USB cable (keep holding the reset button)
- Click "Upload Sketch"
- Wait a second or two until Arduino software says "Uploading..." in the status bar
- Release the reset button
Use these steps to upload any small sketch, Blink example is a good choice.