Passport authentication is causing an issue with access to API call

Trying to create a login authentication system as an entry into web development but the fetch I have to access my login functionality doesn't work. Morgan shows "POST -- ms --". (Works through Postman). As far as I can see my cors system is set up as expected. The API will respond if the passport.authenticate('local') is removed.

authenticate.js

var passport = require('passport');
var LocalStrategy = require('passport-local').Strategy;
var User = require('./models/user');
var JwtStrategy = require('passport-jwt').Strategy;
var ExtractJwt = require('passport-jwt').ExtractJwt;
var jwt = require('jsonwebtoken'); // used to create, sign, and verify tokens


var config = require('./config.js');

exports.local = passport.use(new LocalStrategy(User.authenticate()));
passport.serializeUser(User.serializeUser());
passport.deserializeUser(User.deserializeUser());

exports.getToken = function(user) {
    return jwt.sign(user, config.secretKey,
        {expiresIn: 3600});
};

var opts = {};
opts.jwtFromRequest = ExtractJwt.fromAuthHeaderAsBearerToken();
opts.secretOrKey = config.secretKey;

exports.jwtPassport = passport.use(new JwtStrategy(opts,
    (jwt_payload, done) => {
        console.log("JWT payload: ", jwt_payload);
        User.findOne({_id: jwt_payload._id}, (err, user) => {
            if (err) {
                return done(err, false);
            }
            else if (user) {
                return done(null, user);
            }
            else {
                return done(null, false);
            }
        });
    }));

routes

var express = require('express');
var UserRouter = express.Router();
var passport = require('passport');
var User = require('../models/user')
var authenticate = require('../authenticate');
const cors = require('./cors');
const bodyParser = require('body-parser');
UserRouter.use(bodyParser.json());

UserRouter.route('/login')
.options(cors.corsWithOptions, (req, res) => { res.sendStatus(200); })
.post(cors.cors, passport.authenticate('local'), (req, res) => {  
  console.log(req.body);
  var token = authenticate.getToken({_id: req.user._id});
  res.setHeader('Content-Type', 'application/json');
  res.json({success: true, token: token, status: 'You are successfully logged in!'});
  res.status(200).send()
});
module.exports = UserRouter;

mongoose schema file

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var passportLocalMongoose = require('passport-local-mongoose');

var User = new Schema ({
    firstname : {
        type: String,
        default: ""
    },
    lastname: {
        type: String,
          default: ''
    },
    admin:   {
        type: Boolean,
        default: false
    }
});

User.plugin(passportLocalMongoose);

module.exports = mongoose.model('User', User);

cors file

const express = require('express');
const cors = require('cors');

var whitelist = ['http://localhost:3000', 'http://localhost:3443']
var corsOptionsDelegate = (req, callback) => {
    var corsOptions;
    console.log("Validating origin");
    console.log(req.header('Origin'));
    if(whitelist.indexOf(req.header('Origin')) !== -1) {
        corsOptions = { origin: true };
    }
    else {
        corsOptions = { origin: false };
    }
    callback(null, corsOptions);
};

exports.cors = cors();
exports.corsWithOptions = cors(corsOptionsDelegate);

Front end API call

export const loginUser = (creds) => (dispatch) => {
    console.log("test")
    
    dispatch(requestLogin(creds))
    console.log("attempting login")
    return fetch('http://localhost:3443/users/login', {
        method: 'POST',
        headers: { 
            'Content-Type':'application/json',
        },
        body: JSON.stringify(creds)
    })
    .then(response => {
        console.log("got response 1");
        if(response.ok) {
            return response
        } else {
            console.log("response errored");
            var error = new Error('Error ' + response.status + ': ' + response.statusText);
            error.response = response;
            throw error;
        }
    },
    error => {
        console.log("errored")
        throw error;
    })
    .then(response => response.json())
    .then(response => {
        console.log("got response 2");
        if(response.success) {
            // Successful login
            localStorage.setItem('token', response.token);
            localStorage.setItem('creds', JSON.stringify(creds));
            // TODO dispatch success
            dispatch(receiveLogin(response));
        } else {
            var error = new Error('Error ' + response.status);
            error.response = response;
            throw error;
        }
    })
    .catch(error => dispatch(loginError(error.message)))
}

Does anyone know where I'm going wrong with this? I'm not really getting any useful error messages from my front-end so haven't included. Terminal output upon login attempt

OPTIONS /users/login 204 3.287 ms - 0
POST /users/login - - ms - -