Sorry. We seem to be talking at cross purposes here. I thought we were agreed with the release notes for 1.8.6
core]
- AVR: Set Optiboot as default bootloader for Nano. This is the bootloader installed on new
Arduino Nano boards. If you have a Nano with the old bootloader you must select
Tools > Processor > ATmega328P (Old Bootloader) to upload.
It was when I upgraded that I hit this problem on an old Nano