I'm having a similar problem, except that I'm definitely using the MPU6886 code. There are two files in the examples, almost identical, except for the IMU code. I chose the MPU6886 version, and it never detects any movement. I've also tried the IMU sample, and that sample doesn't show any change - all values are always zero.
Posts made by frogman
RE: Dices example not working on M5Stick C
RE: M5Stick C - Cannot flash firmware
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.