Axios Post pending but MongoDB received information

I’ve been stuck on this for hours would really appreciate if anyone can help!
Below is a registration form, where I post the user info to mongodb.
For some reasons, when I do an axios post, on the network tab in inspect it would show that my request is pending. However, when looking at mongodb, the user is registered in my mongodb collection.
This is my frontend part of it:

async function register(e) {
  e.preventDefault();
  await axios.post("/register", { fname, lname, username, email, password });
}

I have the following backend:

dotenv.config();
mongoose.connect(process.env.MONGO_URL);
const jwtSecret = process.env.JWT_SECRET;
const app = express();
app.use(express.json());
app.use(
  cors({
    credentials: true,
    origin: process.env.CLIENT_URL,
  }),
);
app.post("/register", async (req, res) => {
  const { fname, lname, username, email, password } = req.body;
  try {
    const myUser = await User.create({
      fname,
      lname,
      username,
      email,
      password,
    });
    jwt.sign({ userId: myUser._id }, jwtSecret, {}, (err, token) => {
      if (err) throw err;
      res.cookie("token", token).status(201).json({
        _id: createdUser._id,
      });
    });
  } catch (err) {
    if (err) throw err;
    res.status(500).json("error");
  }
});

I really don’t know how to solve this, Content-Type is set to application/json correctly as the registration form is using cors. Any help would be appreciated!