I am getting this error: Mongoose Error: Operation users.insertOne() buffering timed out after 10000ms when trying to create an instance of User model. Here is the model/User.js

import mongoose from 'mongoose'

const UserSchema = new mongoose.Schema(
  {
    username: {
      type: String,
      min: 3,
      max: 20,
      unique: true,
    },
);

export default mongoose.model("User", UserSchema)

And routes/auth.js (where I send request to create User):

import express from 'express'
import User from "../models/User.js";
const router = express.Router();
//REGISTER
router.post("/register", async (req, res) => {
  try {
    //create new user
    const newUser = new User({
      username: req.body.username,
    });
    //save user and respond
    const user = await newUser.save();
    res.status(200).json("user saved");
  } catch (err) {
    res.status(500).json("error occured")
  }
});
export default router

I double checked and found no error at connecting MongoDB or handling get requests. Only problem is with creating User instance on mongoDB.