Gitbook CSS override doesn't work as expected

Question

I tried to update the default css file, following this suggestion.

To over-ride the Gitbook default styles, create a file called 'styles/website.css` in the root of your gitbook project.

But it never worked. Here is my book.json file.

{
  "title": "Title",
  "description": "description",
  "plugins": ["insert-logo", "language-picker", "hints", "fontsettings","custom-js-css", "collapsible-chapters","back-to-top-button","intopic-toc","hide-published-with","-sharing","copy-code-button","lightbox"],
  "pluginsConfig": {
    "insert-logo": {
      "url": "logo.svg",
      "style": "background:none; height: 50%; width: 50%;"
    },
    "lightbox": {
      "includeJQuery": false,
      "sameUuid": true,
      "options": {
        "resizeDuration": 500,
        "wrapAround": false
      }
    },
    "styles": {
      "website": "styles/website.css"
    }
  }
}

Is there anything wrong? Thanks!