AVRDUDE: stk500_getsync(): not in sync

AVRDUDE: stk500_getsync(): not in sync

This error comes up quite a bit if you are doing prototyping and your Arduino suddenly stops wanting to upload newer program. It’s a confusing error because it lead many people to believe that the Arduino chip itself is damaged and not responding to the upload command.

What is actually happening is a wire somewhere grounding out a pin that the In Circuit Serial Programming (ICSP) needs to use.  All you need to do is use different pins that won’t be grounded out.

Arduino Uno pins that can’t be held to ground
D0, D1

If your Arduino is still not working, it then is either using the wrong COM port or the Arduino driver is corrupt.