react-children expect to receive a single react element child error - react-redux

Question

I was trying to create a survey app using React, Redux. While trying to run the program on localhost:3000, I am getting this React.Children.only expected to receive a single React element child error. I have tried using various solutions which programmers have mentioned elsewhere but nothing has worked. The codes are as below. I must admit I am an absolute tyro as far as programming is concerned
App.js:
import React from 'react';
import {BrowserRouter,Route} from 'react-router-dom';
import Header from './Header';
const Dashboard =() => <h2>Dashboard</h2>;
const SurveyNew =() => <h2>SurveyNew</h2>;
const Landing =() => <h2>Landing</h2>;
const App = () => {
return (
<div>
<BrowserRouter>
<div>
<Header />
<Route exact path= "/" component = {Landing} />
<Route exact path = "/surveys" component= {Dashboard} />
<Route path = "/surveys/new" component={SurveyNew} />
</div>
</BrowserRouter>
</div>
);
};
export default App;
The code of header.js file is as below:
import React, {Component} from 'react';
class Header extends Component {
render () {
return (
<div>
<nav>
<div className = "nav-wrapper">
<a className = "left brand-logo">
Emaily
</a>
<ul className="right">
<li>
<a> Login with Google </a>
</li>
</ul>
</div>
</nav>
</div>
);
}
}
export default Header;