React项目中Navbar.css样式在本地页面不生效问题求助

我正在参加全栈Web开发课程，同时自学React以构建作品集项目，目标是成为前端开发工程师。目前跟着一个两年前的教程入门，这是我遇到的第三个无法解决的问题：Navbar.css的样式在localhost页面完全不显示，且控制台没有任何报错信息。我已经尝试过修改HTML标签、移动/重命名CSS文件、搜索相关解决方案，但都没能解决问题。

以下是项目中的相关代码文件：

components/Navbar.js #

import React, { useState } from 'react';
import Logo from '../images/HHlogo.jpg';
import { Link } from 'react-router-dom';
import "../styles/Navbar.css";

function Navbar() {
  return (
    <div className="Navbar">
      <div className="leftSide">
        <img src={Logo} alt=',' />
      </div>
      <div className="rightSide">
        <Link to="/Home">Home </Link>
        <Link to="/About">About </Link>
        <Link to="/Classes">Classes </Link>
        <Link to="/Gallery">Gallery </Link>
        <Link to="/Trainer">Trainer </Link>
        <Link to="/Testimonial">Testimonial </Link>
        <Link to="/Contact">Contact </Link>
      </div>
    </div>
  );
}

export default Navbar

src/styles/Navbar.css #

.navbar {
  width: 100%;
  height: 100px;
  background-color: #121619;
  display: flex;
  flex-direction: row;
}

.navbar .leftSide {
  flex: 50%;
  height: 100%;
  display: flex;
  align-items: center;
  padding-left: 150px;
}

.navbar .leftSide img {
  width: 70px;
}

.navbar .rightSide {
  flex: 50%;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
}

.navbar a {
  color: white;
  text-decoration: none;
  margin: 20px;
}

.navbar .rightSide button {
  background-color: transparent;
  border: none;
  color: white;
  cursor: pointer;
}

.navbar .rightSide svg {
  font-size: 40px;
}

.navbar #open {
  padding-left: 0px;
}
.navbar #open img {
  display: none;
}

.navbar #close img {
  display: inherit;
}

.navbar #open .hiddenLinks {
  display: inherit;
  margin-left: 30px;
}

.navbar #close .hiddenLinks {
  display: none;
}

.navbar #open a {
  width: 70px;
  margin: 5px;
}
@media only screen and (max-width: 900px) {
  .navbar .rightSide a {
    width: 70px;
  }
  .navbar .leftSide {
    padding-left: 50px;
  }
}

@media only screen and (max-width: 600px) {
  .navbar .rightSide a {
    display: none;
  }

  .navbar .rightSide {
    justify-content: flex-end;
    padding-right: 50px;
  }

  .navbar .rightSide button {
    display: inherit;
  }
}

@media only screen and (min-width: 600px) {
  .navbar .rightSide button {
    display: none;
  }

  .hiddenLinks {
    display: none;
  }
}

src/App.js #

import React from 'react';
import Home from './pages/Home';
import './App.css';
import Navbar from './components/Navbar';
import { BrowserRouter as Router, Route, Routes } from 'react-router-dom';

function App() {
  return (
    <div className="App">
      <Router>
        <Navbar />
        <Routes>
          <Route path="/" exact component={Home} />
        </Routes>
      </Router>
    </div>


  );
}

export default App;

src/index.js #

import React from 'react';
import ReactDOM from 'react-dom';
import App from './App';
import reportWebVitals from './reportWebVitals';

const rootElement = document.getElementById("root");
ReactDOM.render(
  <React.StrictMode>
    <App />
  </React.StrictMode>,
  document.getElementById('root')
);

恳请各位帮忙排查并解决这个问题，谢谢！

内容的提问来源于stack exchange，提问作者Codejester42