Auth0 Authentication Problem

app.log

[2018-07-31T11:58:46.083Z] DEBUG: app/1 on app: ***.***.***.*** ==[GET]==> /auth/callback?code=****************&state=************************
[2018-07-31T11:58:46.084Z] DEBUG: app/1 on app: Processing callback...
[2018-07-31T11:58:46.130Z] DEBUG: app/1 on app: ***.***.***.*** ==[GET]==> /auth/fail
[2018-07-31T11:58:46.131Z]  WARN: app/1 on app: Problem authenticating user. (error=[])

auth.js

"use strict";

const express = require("express");
const passport = require("passport");
const config = require("../config");

const router = express.Router();

router.get("/", passport.authenticate("auth0", {
	clientID: config.auth0.clientID,
	domain: config.auth0.domain,
	redirectUri: config.auth0.callbackURL,
	audience: `https://${config.auth0.domain}/userinfo`,
	responseType: "code",
	scope: "openid email profile",
}), (req, res) => {
	req.app.locals.log.debug("Successful login");
	res.redirect("/");
});

router.get("/logout", (req, res) => {
	req.logout();
	req.app.locals.log.debug("Successful logout");
	res.redirect("/");
});

router.get("/callback", (req, res, next) => {
	req.app.locals.log.debug("Processing callback...");
	next();
}, passport.authenticate("auth0", {
	failureRedirect: "/auth/fail",
	failureFlash: true,
}), (req, res) => {
	req.app.locals.log.debug("Called back from Auth0");
	res.redirect(req.session.returnTo || "/");
});

router.get("/fail", (req, res) => {
	req.app.locals.log.warn({error: req.flash("error")}, "Problem authenticating user.");
	res.render("message", {
		title: "Login Failure",
		message: "There was a problem logging you in. Perhaps the authorization code expired or something else. You could try again or contact support if the problem persists.",
		buttonText: "Try again",
		buttonHref: "/auth",
	});
});

module.exports = router;