Callback.js

import React, { Component } from "react";
import { Redirect } from "react-router-dom";
import auth0Client from "./Auth";

class Callback extends Component {
  state = {
    loading: true
  }

  componentDidMount() {
    auth0Client.handleAuthentication().then(() => this.setState({ loading: false }));
    
  }

  render() {
    
    return this.state.loading ? (
      <p>Loading profile...</p>
    ) : (
      <Redirect to="/" />
    );
  }
}

export default Callback;