Problem with React/Node.js app deployment on Heroku - node.js

Question

I have problem with deployment of my 'TODO APP' on Heroku. I read multiple articles, tutorials and answers on Stack Overflow, but it still doesn't resolve my problem.
This is my index.js file in root directory:
const express = require('express')
const apiRoute = require('./routes/api/index')
const bodyParser = require('body-parser')
const app = express()
app.use(bodyParser.json())
app.use(bodyParser.urlencoded({
extended: true
}))
app.use('/api', apiRoute)
if (process.env.NODE_ENV === 'production') {
app.use(express.static('client/build'))
const path = require('path')
app.get('*', function(req, res) {
res.sendFile(path.resolve(__dirname, 'client', 'build', 'index.html'))
})
}
const PORT = process.env.PORT || 8000
app.listen(PORT)
In the code below you can see scripts in package.json for root directory:
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1",
"client": "npm run start --prefix client",
"server": "nodemon index.js",
"dev": "concurrently --kill-others-on-fail \"npm run server\" \"npm run client\"",
"start": "node index.js",
"heroku-postbuild": "NPM_CONFIG_PRODUCTION=false npm install --prefix client && npm run build --prefix client"
},
In the heroku logs I can see, that "concurrently is not found:
2020-05-18T19:00:50.438389+00:00 app[web.1]: sh: 1: concurrently: not found
2020-05-18T19:00:50.443535+00:00 app[web.1]: npm ERR! code ELIFECYCLE
2020-05-18T19:00:50.444083+00:00 app[web.1]: npm ERR! syscall spawn
2020-05-18T19:00:50.444495+00:00 app[web.1]: npm ERR! file sh
2020-05-18T19:00:50.444972+00:00 app[web.1]: npm ERR! errno ENOENT
2020-05-18T19:00:50.446708+00:00 app[web.1]: npm ERR! to-do-app#1.0.0 start: `concurrently "npm run server" "npm run client"`
2020-05-18T19:00:50.446990+00:00 app[web.1]: npm ERR! spawn ENOENT
I have tried multiple things, but none of them work. Any ideas please?

Answer 1

In your package.json maybe the script dev is causing an issue.
Try clearing all the scripts and only leave
"start" : "node server.js"
"test": "echo "Error: no test specified" && exit 1"
"heroku-postbuild": "cd client && npm install && npm run build"