React routing doesn't work when changing URL manually | React-router 4

My routing works fine when the url is changed via the Link React-router component. However, if I try to change the URL manually in the browser, it hits a 404 error.

Below is the routes.js file

import React from "react";
import {Route, Switch, NotFoundRoute} from 'react-router-dom';
import App from "./components/app.jsx";
import HomePage from "./components/homePage.jsx";
import AboutPage from "./components/about/aboutPage.jsx";
import AuthorPage from "./components/authors/authorPage.jsx";
import ManageAuthorPage from "./components/authors/manageAuthorPage.jsx";
import NotFoundPage from "./components/notFoundPage.jsx";

var routes = (
    <App>
        <Switch>
            <Route name="home" exact path="/" component={HomePage} />
            <Route name="authors" exact path="/authors" component={AuthorPage} />
            <Route name="addAuthor" exact path="/author" component={ManageAuthorPage} />
            <Route name="manageAuthor" path="/author/:id" component={ManageAuthorPage} />
            <Route name="about" exact path="/about" component={AboutPage} />
            <Route component={NotFoundPage} />
        </Switch>
    </App>
);

export default routes;

      

        
        
        
      

    

Main.js file containing BrowserRouter

import React from 'react';
import ReactDOM from 'react-dom';
import {BrowserRouter} from 'react-router-dom';
import routes from './routes.jsx';
import InitializeActions from './actions/initializeActions';

InitializeActions.initApp();

ReactDOM.render(<BrowserRouter>{routes}</BrowserRouter>, document.getElementById('app'));

      

        
        
        
      

    

and a header.jsx file containing the navigation bar

import React from 'react';
import {Link} from 'react-router-dom';

class Header extends React.Component {
    render() {
        return (
            <nav className="navbar navbar-default">
                <div className="container-fluid">
                    <Link to="/" className="navbar-brand">
                        <img src="../../images/pluralsight-logo.png"/>
                    </Link>
                    <ul className="nav navbar-nav">
                        <li><Link to="/">Home</Link></li>
                        <li><Link to="authors" ref={(comp) => { window.authorsTab=comp }}>Authors</Link></li>
                        <li><Link to="about">About</Link></li>
                    </ul>
                </div>
            </nav>
        );
    }
}

export default Header;

      

        
        
        
      

    

Gulpfile.js

"use strict";

var gulp = require('gulp');
var connect = require('gulp-connect'); //Runs a local dev server
var open = require('gulp-open'); //Opens a URL in a web browser
var browserify = require('browserify'); //Bundle JS
var reactify = require('reactify'); //Transforms react JSX to JS
var source = require('vinyl-source-stream'); //Use-conventional text streams with gulp
var concat = require('gulp-concat'); //concatnates files
var lint = require('gulp-eslint'); //lint our js files including jsx
var babelify = require("babelify");
var browserSync = require("browser-sync");

var config = {
  port: 9005,
  devBaseUrl: 'http://localhost',
  paths: {
    html: './src/*.html',
    js: './src/**/*.js*',
    images: './src/images/*',
    css: [
      'node_modules/bootstrap/dist/css/bootstrap.min.css',
      'node_modules/bootstrap/dist/css/bootstrap-theme.min.css',
      './src/dependencies/*.css',
      'node_modules/toastr/build/toastr.css'
    ],
    dist: './dist',
    mainJs: './src/main.jsx'
  }
}

//start a local dev server
gulp.task('connect', function() {
  connect.server({
    root: ['dist'],
    port: config.port,
    base: config.devBaseUrl,
    livereload: true
  });
});

//opens the URL in browser
gulp.task('open', ['connect'], function() {
  gulp.src('dist/index.html')
    .pipe(open({uri: config.devBaseUrl + ':' + config.port + '/'}));
});

//get all the html files from 'src', bundle them and place inside 'dist' and reload the server
gulp.task('html', function() {
  gulp.src(config.paths.html)
    .pipe(gulp.dest(config.paths.dist))
    .pipe(connect.reload());
});

gulp.task('js', function() {
  browserify(config.paths.mainJs)
    .transform(babelify, {presets: ["es2015", "react"]})
    .bundle()
    .on('error', console.error.bind(console))
    .pipe(source('bundle.js'))
    .pipe(gulp.dest(config.paths.dist + '/scripts'))
    .pipe(connect.reload());
});

gulp.task('css', function() {
  gulp.src(config.paths.css)
    .pipe(concat('bundle.css'))
    .pipe(gulp.dest(config.paths.dist + '/css'));
});

gulp.task('images', function() {
  gulp.src(config.paths.images)
    .pipe(gulp.dest(config.paths.dist + '/images'))
    .pipe(connect.reload());
});

gulp.task('lint', function() {
  return gulp.src(config.paths.js)
    .pipe(lint({configFile: 'eslint.config.json'}))
    .pipe(lint.format());
});

//watch any changes in html files
gulp.task('watch', function() {
  gulp.watch(config.paths.html, ['html']);
  gulp.watch(config.paths.js, ['js', 'lint']);  
  gulp.watch(config.paths.css, ['css']);  
});

//the default task
gulp.task('default', ['html', 'js', 'css', 'images', 'lint', 'open', 'watch']);

      

        
        
        
      

    

I've tried to find solutions from several sources, but everyone seems to follow a similar approach as mine! Please look. Thanks in advance:)