ERROR: Class not defined.

I’m just following the tutorial below. https://foxdot.org/installation/

My environment is macOS 10.14.6, python3.6

I did

1, brew install SuperCollider 3.11.1.

2, pip install FoxDot 0.8.11

3, installed sc3-plugins-3.11.0-macOS.zip from its official page

And I activate SuperCollider and enter Quarks.install("FoxDot") then it’s installed successfully. But when I do FoxDot.start, it says there is no class defined.

ERROR: Class not defined.
  in interpreted text
  line 1 char 6:

  DotFox.start 

I don’t know why this happens and it takes me hours to know what’s really happening. Any advice will be appreciated.