Passport js authentication returning 404

My passport.authenticate request is returning a 404 for some reason, and I have literally no clue why. My routes are definitely correct, pretty sure (de)serialization is correct and user details do get stored in database; however, returns a 404 when details ARE stored, and a 401 when details are incorrect (as expected). I am using mongodb/mongoose Any help would be appreciated.

passport.js:

const passport = require('passport');
const User = require('../models/user');
const LocalStrategy = require('passport-local').Strategy;

passport.serializeUser((user, done) => {
    done(null, user.id);
});

passport.serializeUser((id, done) => {
    User.findById(id, (err, user) => {
        done(err, user);
    })
});

passport.use('local.register', new LocalStrategy({
    usernameField: 'username',
    passwordField: 'password',
    passReqToCallback: true
}, (req, username, password, done) => {
    User.findOne({ $or: [{'email': req.body.email}, {'username': username}]}, (err, user) => {
        if(err || user) {
            return done(err);
        }
        if(user) {
            return done(null, false, {message: 'Email or username in use'});
        }
        const newUser = new User();
        newUser.username = username;
        newUser.email = req.body.email;
        newUser.password = newUser.encryptPassword(password);
        newUser.save((err, data) => {
            if(err) {
                return done(err);
            }
            //CODE REACHES THIS POINT, HAVE DEBUGGED
            return done(null, newUser);
        });
    });
}));

user.js:

const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const bcrypt = require('bcrypt-nodejs');

const userSchema = new Schema({
    username: {type: String, required: true},
    email: {type: String, required: true},
    password: {type: String, required: true},

});

userSchema.methods.encryptPassword = function() {
    return bcrypt.hashSync(this.password, bcrypt.genSaltSync(5), null);
};

userSchema.methods.validPassword = function(password) {
    return bcrypt.compareSync(this.password, password);
};

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

registration.js:

const express = require('express');
const router = express.Router();
const mongodb = require('mongodb');
const passport = require('passport');

router.post('/', passport.authenticate('local.register'));

module.exports = router;

app.js:

const express = require('express');
const path = require('path');
const logger = require('morgan');
const cookieParser = require('cookie-parser');
const bodyParser = require('body-parser');
const sassMiddleware = require('node-sass-middleware');
const cors = require('cors');
const mongoose = require('mongoose');
const mongo = require('mongodb');
const passport = require('passport');

const python = require('./routes/python');
const register = require('./routes/registration');

const app = express();
const dbURL = 'mongodb://localhost:27017/aiarena';

mongoose.connect(dbURL);
require('./config/passport');

app.use(cors());

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');

// uncomment after placing your favicon in /public
// app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));
app.use(cookieParser());
app.use(passport.initialize());
app.use(passport.session());
app.use(sassMiddleware({
  src: path.join(__dirname, 'public'),
  dest: path.join(__dirname, 'public'),
  indentedSyntax: true, // true = .sass and false = .scss
  sourceMap: true,
}));

//Routes
app.use('/', express.static(path.join(__dirname, '../client/')));
app.use('/python', python);
app.use('/register', register);

...

via Fraser Price