导航无法在react-bootstrap中突然工作

Question

我的反应应用程序曾经使用react-bootstrap，现在突然导航无效。这是我的package.json。目前，它只显示“室友”品牌，但没有其他项目，如登录或联系或关于它旁边有一个小按钮，当我点击按钮，它扩展一秒钟，菜单显示和再次消失，当屏幕很小时，汉堡包菜单也不显示。

{
 "name": "newreactstuff",
 "version": "0.1.0",
 "private": true,
 "dependencies": {
 "react": "^16.2.0",
 "react-bootstrap": "^0.32.1",
 "react-dom": "^16.2.0",
 "react-router": "^4.2.0",
 "react-router-dom": "^4.2.2",
 "react-scripts": "1.1.1"
  },
 "scripts": {
 "start": "react-scripts start",
 "build": "react-scripts build",
 "test": "react-scripts test --env=jsdom",
 "eject": "react-scripts eject"
  },
"proxy": "http://localhost:3001/"
}

这是我的导航组件

import React, { Component } from 'react';
import {
  Link
 } from 'react-router-dom';
import { NavItem } from 'react-bootstrap';
import { MenuItem } from 'react-bootstrap';
import { NavDropdown } from 'react-bootstrap';
import { Nav, Navbar, NavItem, NavDropdown, MenuItem, FormControl, FormGroup, 
Button } from 'react-bootstrap';


class Navigation extends Component {

render() {
 return (
  <Navbar inverse collapseOnSelect>
   <Navbar.Header>
    <Navbar.Brand>
     <Link to="/">Roommates</Link>
   </Navbar.Brand>
   <Navbar.Toggle />
 </Navbar.Header>
 <Navbar.Collapse>
   <Nav pullRight>
      <li><Link to="/">Sign In</Link></li>
      <li><Link to="/contact">Contact</Link></li>
      <li><Link to="/about">About</Link></li>
   </Nav>
  </Navbar.Collapse>
 </Navbar>
     )
   }
 }

export default Navigation;