Accessing Node server remotely from React page

I have created a site using Create React App on the frontend and Node express on the back. I then hosted React on IIS and ran Node as a windows service on the backend.

When running the app I set my callback paths in React (REACT_APP_HOST) to "localhost" and in the node my routes are "/routeName". This being said, the first path called is ${REACT_APP_HOST}/sitemap and the receiving path on the server is router.use('/siteMap', (req, res, next) => siteMapController(req, res, next));.

On the local server, using it as a client, this works perfectly. On a remote client (same domain) I am getting a 404 error.

The next step I tried was changing REACT_APP_HOST to "", making the resulting call to "/sitemap". This has stopped the functioning even on localhost.

Here is my code (app.js, sitemap fetch and server.js). Hoping that someone can give me a clue as to where I am going wrong.

//app.js

var createError = require('http-errors');
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser')
var logger = require('morgan');
var cors = require('cors');
var nodeSSPI = require('express-node-sspi');
let routeList = require('./routes/routeList');
let FileLoader = require('./Controllers/FileLoader');

var app = express();

app.use(bodyParser.json({ limit: '400000' }));
app.use(cors({
  origin:['http://localhost', 'http://intranet-test', 'http://intranet'],
  credentials: true
}));
app.use(express.static(path.join(__dirname,'../public')));
app.options('*', cors()); // include before other routes
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'pug');

//https://www.npmjs.com/package/yarn 
app.use(nodeSSPI({
  retrieveGroups: false,
  offerBasic: false,
  authoritative: true,

}));

app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

routeList(app);

// catch 404 and forward to error handler
app.use(function (req, res, next) {
  console.log(req.originalUrl);
  console.log(req.method)
  next(createError(404));
});

// error handler
app.use(function (err, req, res, next) {
  console.log(err);
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});

module.exports = app;

//sitemap fetch
export const fetchInit = () => {
    return ({
        method: 'GET'
        , headers: {
            'Content-Type': 'application/json'
        }
        , credentials: 'include'
    })
};

export const Sitemap_Fetch = () => (dispatch) => {
    dispatch({
        type: ActionTypes.SITEMAP_LOADING
    });
    var myReq = new Request(`${process.env.REACT_APP_HOST}/siteMap`, fetchInit());//?' + params

    return fetch(myReq)
        .then((response) => {
            // if (response.ok) {
            return response;
            // }
            // else {
            //     var error = new Error("Error " + response.statusText);
            //     error.response = response;
            //     throw error;
            // }
        },
            (error) => {
                var err = new Error(error.message);
                throw err;
            }
        )
        .then(response => response.json())
        .then((data) => {
            try {
                dispatch({
                    type: ActionTypes.SITEMAP_LOADED,
                    payload: data
                })
                return data;
            }
            catch (ex) { throw ex }
        })
        .catch((err) => {
            return dispatch({
                type: ActionTypes.SITEMAP_FAILED,
                payload: err.message
            })
        });
}

//server.js
#!/usr/bin/env node

/**
 * Module dependencies.
 */

var app = require('./app');
var debug = require('debug')('node-backend:server');
var http = require('http');


/**
 * Get port from environment and store in Express.
 */

var port = normalizePort('3000');
app.set('port', port);

/**
 * Create HTTP server.
 */

var server = http.createServer(app);

/**
 * Listen on provided port, on all network interfaces.
 */

server.listen(port, '0.0.0.0');
server.on('error', onError);
server.on('listening', onListening);
server.on('request',test=>{console.log(test)})
/**
 * Normalize a port into a number, string, or false.
 */

function normalizePort(val) {
  var port = parseInt(val, 10);

  if (isNaN(port)) {
    // named pipe
    return val;
  }

  if (port >= 0) {
    // port number
    return port;
  }

  return false;
}

/**
 * Event listener for HTTP server "error" event.
 */

function onError(error) {
  if (error.syscall !== 'listen') {
    throw error;
  }

  var bind = typeof port === 'string'
    ? 'Pipe ' + port
    : 'Port ' + port;

  // handle specific listen errors with friendly messages
  switch (error.code) {
    case 'EACCES':
      console.error(bind + ' requires elevated privileges');
      process.exit(1);
      break;
    case 'EADDRINUSE':
      console.error(bind + ' is already in use');
      process.exit(1);
      break;
    default:
      throw error;
  }
}

/**
 * Event listener for HTTP server "listening" event.
 */

function onListening() {
  var addr = server.address();
  console.log(addr)
  var bind = typeof addr === 'string'
    ? 'pipe ' + addr
    : 'port ' + addr.port;
  debug('Listening on ' + bind);
  console.log('Listening on ' + bind);
}

Finally I am adding the .env file from my React site

BROWSER=none
SKIP_PREFLIGHT_CHECK=true
REACT_APP_HOST=http://localhost
PORT=80

This works as is. When I change REACT_APP_HOST to nothing it stops functioning.

THanks.