TOC toggle in HTML render not working

Notebook
1

I have a problem with my jupyter book html render where the headers on the side bar menu does not expand/collapse. I am having this issue with the chapters/sections.

Here is my _toc.yml:

format: jb-book
root: intro
parts:
- captions: Mathematical Concepts
  chapters:
  - file: index_m
    sections:
    - file: Probability
    - file: linear_algebra
  - file: index_ul
    sections:
    - file: libraries

I should have index_m wrapping the content from the sections probability and linear algebra but it does not expand or collapse.

I am using the latest version of Jupyter 1.0. The HTML render is not working well.