Fetch not retrieving values

I am creating a website using HTML, CSS, JS and Python flask but for some reason, when I fetch data from the flask, everything in python works perfect but then the JS does not get the result of the fetch, to be efficient I will just show the JS file and Python code, if you need more ask me for it but I think that should be fine.

const menu = document.querySelector('#mobile-menu');
const menuLinks = document.querySelector('.navbar__menu');

menu.addEventListener('click', function() {
  menu.classList.toggle('is-active');
  menuLinks.classList.toggle('active');
});

var imgElement = document.getElementById("signUpButton");

imgElement.addEventListener('click', function(){
  console.log("Sign Up Image clicked!");
  var username = document.getElementById("username").value;
  var email = document.getElementById("email").value;
  var password = document.getElementById("password").value;

  console.log({username, email, password});

  fetch('http://127.0.0.1:5000/signup', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      username: username,
      email: email,
      password: password
    })
  })
  console.log("hey")
  .then(response => response.json())
  .then(data => {
    if (data.success == false){
      document.getElementById("resultMessage").innerHTML = "User already exists, please sign in with your account or create a new one";
    }
  })
  .catch((error) => {
    console.error('Error', error);
  })
});

from flask import Flask, request, jsonify
import json
import os
from flask_cors import CORS

app = Flask(__name__)
CORS(app, resources={r"/*": {"origins": "http://localhost:63342"}})

USERS_FILE = os.path.join(os.path.dirname(__file__), 'users.json')


def load_users():
    if os.path.exists(USERS_FILE):
        with open(USERS_FILE, 'r') as f:
            return json.load(f)
    return []


def save_users(users):
    with open(USERS_FILE, 'w') as f:
        json.dump(users, f, indent=4)


@app.route('/signup', methods=['POST'])
def signup():
    data = request.get_json()
    print("Received data:", data)
    username = data['username']
    email = data['email']
    password = data['password']

    users = load_users()

    if not username or not email or not password:
        print("hi")
        return jsonify({"success": False, "message": "Please enter valid username, email, and password."})
    elif any(user['username'] == username or user['email'] == email for user in users):
        return jsonify({"success": False, "message": "Username or email already exists, please try again!"})
    else:
        users.append({"username": username, "email": email, "password": password})
        print("Updated users list:", users)
        save_users(users)

        return jsonify({"success": True, "message": "User registered successfully!"})


if __name__ == '__main__':
    app.run(debug=True)