'Search' Plugin didn't work.

[FlipWind]

I have add a plugin on my website. But it did't work.

The file: /program/docs/config.js

import { defaultTheme } from '@vuepress/theme-default'
import { searchPlugin } from '@vuepress/plugin-search'

export default({
  lang: 'zh-CN',
  title: 'iChe | Program Docs',
  description: 'The Online Docs. Have fun!',
  plugins: [
    searchPlugin({
    }),
  ],
  theme: defaultTheme({
    navbar: [
      {
        text: 'Foo',
        link: '/foo/',
      },
      // NavbarGroup
      {
        text: 'Group',
        children: ['/group/foo.md', '/group/bar.md'],
      },
    ],
  }),
})

I dont know how to fix it.
And this is result:

[FlipWind]

I have updated all the things. Fixed it.