Acces to XMLHttpRequest at 'https://api-link/login' from origin 'http://localhost/3000' has been blocked by cors policy. (React, , firebase, JWT))

Question

When I try to implement a secure login system in React application with firebase using JSON Web Token (JWT) I am getting this error: Acces to XMLHttpRequest at 'https://api-link/login' from origin 'http://localhost/3000' has been blocked by cors policy. I am using node js for the backend.

I also use cors middleware:

const cors = require("cors");
app.use(cors());

My Backend Code:

  const verifyJWT = (req, res, next) => {
  const authHeader = req.headers.authorization;
  console.log(authHeader);

  if (!authHeader) {
    return res.status(401).send({
      message: "unauthorized access",
    });
  }
  const token = authHeader.split(" ")[1];
  jwt.verify(token, process.env.ACCESS_TOKEN_SECRET, (err, decoded) => {
    if (err) {
      return res.status(403).send({ message: "forbidden access" });
    } else {
      console.log("decoded", decoded);
      req.decoded = decoded;
      next();
    }
  });
};

Backend login route

  app.post("/login", async (req, res) => {
  const user = req.body;
  const accessToken = jwt.sign(user, process.env.ACCESS_TOKEN_SECRET, {
    expiresIn: "1d",
  });
  res.send({ accessToken });
});

My Client-side code:

const handleSubmit = async (e) => {    
e.preventDefault();
await signInWithEmailAndPassword(values.email, values.password);
const email = values.email;

const { data } = await axios.post(
  "https://stark-sands-89628.herokuapp.com/login",
  { email }
);
localStorage.setItem("accessToken", data.accessToken)};