passport's req.isAuthenticated always returning false, even when I hardcode done(null, true)

I'm trying to get my Passport local strategy working.

I've got this middleware set up:

passport.use(new LocalStrategy(function(username, password, done) {
    //return done(null, user);
    if (username=='ben' && password=='benny'){
        console.log("Password correct");
        return done(null, true);
    }
    else
        return done(null, false, {message: "Incorrect Login"});
}));

but then in here

app.use('/admin', adminIsLoggedIn, admin);

function adminIsLoggedIn(req, res, next) {

    // if user is authenticated in the session, carry on 
    if (req.isAuthenticated())
        return next();

    // if they aren't redirect them to the home page
    res.redirect('/');
}

it always fails and redirects to the home page.

I can't figure out why this is happening? Why won't it authenticate?

In my console I can see that's Password Correct is printing. Why won't it work?

I had a similar issue. Could be due to the express-session middleware needed for passport. Fixed it by using middlewares in the following order: (Express 4)

var session = require('express-session');

// required for passport session
app.use(session({
  secret: 'secrettexthere',
  saveUninitialized: true,
  resave: true,
  // using store session on MongoDB using express-session + connect
  store: new MongoStore({
    url: config.urlMongo,
    collection: 'sessions'
  })
}));

// Init passport authentication 
app.use(passport.initialize());
// persistent login sessions 
app.use(passport.session());