MongoServerError: bad auth : Authentication

Hi im making an app with node js, mongo db and im deploying in vercel, so i made the aplication and i tested on mode dev and was okay but when execute the comand “now” and see the site it appear a error 500 and im seein from vercel and
the page of vercel function log

it say that bad auth but i tried that on mode dev, so i dont know why is the problem, this is the index.json when i connect

const express =require('express')
const mongoose =require('mongoose')
const bodyParser= require('body-parser')
const cors= require('cors')
const meals=require('./routes/meals')
const orders=require('./routes/order')

const app=express()
app.use(bodyParser.json())
app.use(cors())
mongoose.connect(process.env.MONGODB_URI)



app.use('/api/meals',meals)
app.use('/api/order',orders)


module.exports=app;

and i created a file .env and i put this

MONGODB_URI=mongodb+srv://almuerzimaster:[email protected]/myFirstDatabase?retryWrites=true&w=majority