I was having the same problem, but it's working now. I use a Macbook Pro running Catalina.
Received my M5StickC today, and it looks great, but the Arduino AVR ISP and AVR ISP II programmers couldn't connect to it. I installed updated CP210X drivers, but that didn't help. Then I tried the suggestions from m5stack above, and when I connected G0 to GND, then clicked the "Upload" button in the Arduino IDE, it worked.