Error H10: Application Error on an app that used to work perfectly on heroku

I’ve been working on an application for a couple of months while learning node js and express. It used to work fine on heroku but after my latest changes it stopped working, showing application error which happened many times before but this time I can’t figure out what’s going wrong. I’m pretty sure the deploy is done well, as it worked a couple of days ago and stopped working now, so the problem is likely somewhere in all of the express code.

Here is my entry point (app.js):

    const mainRoutes = require('./routes/mainRoutes');
const marketplaceRoutes = require('./routes/marketplaceRoutes');
const usersRoutes = require('./routes/usersRoutes');
const isUserLogged = require('./middlewares/isUserLogged');

const express = require('express');
const path = require('path');
const session = require('express-session');
const cookieParser = require('cookie-parser');

let app = express();

app.set('view engine', 'ejs');
app.set('views', path.join(__dirname, '/views'));

const publicPath = path.resolve(__dirname, '..', './public');
const viewsPath = path.resolve(__dirname, './views')

app.use(express.urlencoded({ extended: false }));
app.use(express.json());
app.use(express.static(publicPath)); //Hacer publica la carpeta Public
app.use(express.static(viewsPath)); //Hacer publica la carpeta views

app.use(session({
    secret: "secreto starknights",
    resave: true,
    saveUninitialized: false,
})); //Configurar session

app.use(cookieParser());

//app.use(userCookie);

app.use('/', isUserLogged, mainRoutes);
app.use('/marketplace', isUserLogged, marketplaceRoutes);
app.use('/users', isUserLogged, usersRoutes);

app.listen(process.env.PORT || 3000, () => {
    console.log('Servidor corriendo en el puerto 3000');
});

also here’s my Procfile:

web: node src/app.js

I’ll also leave a link to the github repository where this is all located. By the way the app works perfectly fine when hosted locally. The problem comes only when deployed to heroku. Thanks