The first thing we need to do is determine which is the correct Tools > Processor menu selection for your Nano. For official Arduino Nano boards manufactured by Arduino which were purchased in 2018 or 2019, the correct selection is Tools > Processor > ATmega328P. For Nano clones or derivatives made by other companies or official Arduino Nano boards purchased before 2018, the correct selection is Tools > Processor > ATmega328P (Old Bootloader). Make sure you have the right Tools > Processor menu selection.
Remove any connections to pins 0 and 1. These pins are used for communication with your computer, including uploads. Connecting anything to these pins can interfere with uploads.
Make sure you have selected the port of your Nano from the Tools > Port menu.
If you don’t know which port is your Arduino, you can find it like this:
- Unplug your Arduino board from the computer.
- Tools > Port
- Note the ports, if any, listed in the menu.
- Close the Tools menu
- Plug your Arduino board into the computer.
- Tools > Port - The new port listed in the menu is your Arduino board.