Uncaught (in promise) Error: Network Error at createError (createError.js:16) at XMLHttpRequest.handleError (xhr.js:117)

I'm working on a chat application project and whenever I try to sign in, it gives me these errors. Every single time I try to Sign In to app the it gives errors. I'm using axious, Stream API, Cookies, Expressjs, and React.

Error:

POST http://localhost:5000/auth/signup net::ERR_CONNECTION_REFUSED

createError.js:16 Uncaught (in promise) Error: Network Error
    at createError (createError.js:16)
    at XMLHttpRequest.handleError (xhr.js:117)

Authentication file:

import React, { useState } from 'react';
import Cookies from 'universal-cookie';
import axios from 'axios';

import signinImage from '../assets/signup.jpg';

const cookies = new Cookies();

const initialState = {
    fullName: '',
    username: '',
    password: '',
    confirmPassword: '',
    phoneNumber: '',
    avatarURL: '',
}

const Auth = () => {
    const [form, setForm] = useState(initialState);
    const [isSignup, setIsSignup] = useState(true);

    const handleChange = (e) => {
        setForm({ ...form, [e.target.name]: e.target.value });
    }

    const handleSubmit = async (e) => {
        e.preventDefault();

        const { username, password, phoneNumber, avatarURL } = form;

        const URL = 'http://localhost:5000/auth';
        // const URL = 'https://medical-pager.herokuapp.com/auth';

export default Auth

Server Side:

import express, { json, urlencoded } from 'express';
import cors from 'cors';

import authRoutes from "./routes/auth.js";

const app = express();
const PORT = process.env.PORT || 5000;

require('dotenv').config();

const accountSid = process.env.TWILIO_ACCOUNT_SID;
const authToken = process.env.TWILIO_AUTH_TOKEN;
const messagingServiceSid = process.env.TWILIO_MESSAGING_SERVICE_SID;
const twilioClient = require('twilio')(accountSid, authToken);

app.use(cors());
app.use(json());
app.use(urlencoded());

app.get('/', (req, res) => {
    res.send('hello, world');
});