Tengo un problema de cors en mi código aunque no hubo problemas cuando todo se ejecutaba en el host local

Código en el servidor

 import bodyParser from 'body-parser'; import bcrypt from 'bcrypt-nodejs'; import cors from 'cors'; import knex from 'knex'; import handleRegister from './controllers/register.js'; import handleSignin from './controllers/signin.js'; import handleProfileGet from './controllers/profile.js'; import {handleImage, handleApiCall} from './controllers/image.js'; const db = knex({ client: 'pg', connection: { connectionString: process.env.DATABASE_URL, ssl: { rejectUnauthorized: false } }); const app = express(); app.use(bodyParser.json()); app.use(cors( origin: '*', credentials:true )); app.get('/', (req,res) => {res.send('it is working')}) app.post('/signin', (req, res) => { handleSignin(req, res, db, bcrypt) }) app.post('/register', (req, res) => { handleRegister(req, res, db, bcrypt) }) app.get('/profile/:id', (req, res) => { handleProfileGet(req, res, db)}) app.put('/image', (req, res) => { handleImage(req, res, db)}) app.post('/imageurl', (req, res) => { handleApiCall(req, res)}) app.listen(process.env.PORT || 3000, () => { console.log(`app is running on port ${process.env.PORT}`); })

mi solicitud de publicación

 onSubmitSignIn = () => { fetch('https://intense-lowlands-80632.herokuapp.com/signin', { method:'post', headers:{'Content-Type': 'application/json'}, body:JSON.stringify({ email: this.state.signInEmail, password: this.state.signInPassword }) }) .then(response => response.json()) .then(user => { if (user.id) { this.props.loadUser(user) this.props.onRouteChange('home') } }) }

error

2021-09-21T10:03:17.603744+00:00 heroku[router]: at=código de error=H10 desc="Aplicación bloqueada" method=OPTIONS path="/signin" host=intense-lowlands-80632.herokuapp.com request_id=b146be27-0bd2-43ac-bcb9-b0661e6a3085 fwd="188.25.95.60" dyno= conectar= servicio= estado=503 bytes= protocolo=https