Boards 1.6.21 not working for MacOS 10.13

Development Tools IDE 1.x
1

I have spent a day trying to get my Nano connected. I have treid one using the CH340 chip (driver loaded) and one using the FTDI chip.

With Boards 1.6.21 for the Nano loaded, neither works and I just get upload errors.

I downgraded to 1.6.19 and all is well.

TAKE NOTE

2

There was a change made in Arduino IDE 1.6.21 that requires you to select Tools > Bootloader > ATmega328P (Old Bootloader) if you have a clone Nano (such as the ones with the CH340) or an old official Nano.