Secure specific react page using keycloak

I am building a demon project of authentication whith Keycloak into a react project. I have one public page and a private one. The private page check if the user is logged in and display a button to log in or to log out, depending the connection state. This part works well. When I click on the log in button I am redirected to the Keycloak portal. After login, I am redirected to the private page and I can log out with the apropriated button.

But when I navigate to the public page and go back to the private, or just refreshing the private page, the connection seems to be out. Then I click on the log in button and the connection come back, without been redirected to the keycloak portal.

There the private page :

import React from "react";
import Nav from "../modules/Nav";
import RenderAnonymous from "../modules/RenderAnonymous";
import RenderAuthenticated from "../modules/RenderAuthenticated";
import UserService from "../services/UserService";

const Private = () => {
    return (
        <>
            <Nav/>
            <RenderAnonymous>
                <p>Il faut s'authentifier</p>
                <button onClick={UserService.doLogin} className="btn login-btn">Se connecter</button>
            </RenderAnonymous>
            <RenderAuthenticated>
                <p>User info</p>
                <button onClick={UserService.doLogout} className="btn login-btn">Déconnexion</button>
            </RenderAuthenticated>
            <div className="private">
                <h2>Page privée</h2>
            </div>
        </>
    );
};

export default Private;

RenderAnonymous and RenderAuthenticated are the same expect the authentication condition :

import UserService from "../services/UserService";

const RenderAuthenticated = ({children}) => {
    if (UserService.isAuthenticated()) {
        return (children);
    }
    return null;
};


export default RenderAuthenticated;

UserService :

import keycloak from "keycloak-js";

const KC = new keycloak("/keycloak.json");

const initKeycloak = (authenticatedCllback) => {
    KC.init({
        onLoad: "check-sso"
    }).then((auth)=>{
        if (auth) {
            console.info("Already logged in");
        } else {
            console.info("Need to log in");
        }
        authenticatedCllback();
    }).catch((err)=>{
        console.error(err);
    });
}

const doLogin = () => {
    return KC.login();
}

const doLogout = () => {
    return KC.logout();
}

const isAuthenticated = () => {
    return KC.authenticated;
}

const UserService = {
    initKeycloak,
    doLogin,
    doLogout,
    isAuthenticated,
};

export default UserService;

The inistialization of keycloak is launched from index.js :

import React from "react";
import ReactDOM from "react-dom";
import App from "./App";
import UserService from "./services/UserService";

const renderApp = () => ReactDOM.render(<App/>,document.getElementById("root"));

UserService.initKeycloak(renderApp);

I don't understand where is the problem... Is it a problem of flow ? https://www.keycloak.org/docs/latest/securing_apps/index.html#_javascript_implicit_flow

From my point of view, you should integrate the keycloak object (and the UserService) into react handling. At the moment it seems to live outside of your <App/>.

For example you can use React context to hold the keycloak instance. But you do not need to implement this yourself. There is already a library called react-keycloak which implements this approach.