NODE API runs on localhost but doesn't run on Vercel - node.js

Question

I'm trying to upload a node app to Vercel and use as API but I'm getting an This Serverless Function has crashed. error message. The fact that I can run it with no problems in localhost, and the fact that the build log doesn't throw an error, I can't seems to find the problem.
Here is a full Screenshot:
vercel app
And here is my index.js:
const express = require(`express`);
var cors = require('cors')
const app = express();
app.use(cors())
const bodyParser = require('body-parser')
const mongoose = require("mongoose")
require("dotenv").config();
const config = require('config');
const dbConfig = config.get("MT.dbConfig.dbName")
mongoose.connect(dbConfig, {
}).then(() => {
console.log('Database connected.')
}).catch((err)=> console.log('Something went wrong with the database : ' + err))
mongoose.Promise = global.Promise;
app.use(bodyParser.json())
app.use('/', require('./api/v1/api'))
app.use((err, req, res, next) =>{
res.status(422).send({
error: err._message
})
})
const PORT = 5001;
app.listen(PORT, () => console.log("API is running."))
And here is my package.json:
{
"name": "hidden",
"version": "1.0.0",
"description": "",
"main": "index.js",
"engines": {
"node": "14.x"
},
"scripts": {
"start": "vercel dev",
"deploy": "vercel deploy --prod"
},
"author": "hidden",
"license": "ISC",
"dependencies": {
"body-parser": "^1.19.0",
"config": "^3.3.6",
"cors": "^2.8.5",
"dotenv": "^10.0.0",
"express": "^4.17.1",
"mongoose": "^6.0.13",
"vercel": "^23.1.2"
},
"devDependencies": {
"nodemon": "^2.0.15"
}
}