code=H10 desc="App crashed" can't find solution why it happened - node.js

Question

So I deployed my third app to heroku but to my surprise the app is not working, it's the first time when I get this kind of error:
code=H10 desc="App crashed"
At first I forgot to set my port variable like this: const port = process.env.PORT || 5000;
And then listen to it like this:
server.listen(port, () => {
console.log('Server is runing on port 5000');
});
But even when I set up port variable I still get the same error and I don't know what can cause this error.
2018-10-04T15:12:29.405064+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/" host=m-o-d.herokuapp.com request_id=430f142b-4820-410b-865b-cc6bffae2fa5 fwd="195.12.167.97" dyno= connect= service= status=503 bytes= protocol=https
2018-10-04T15:12:29.654458+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=m-o-d.herokuapp.com request_id=30ff6c29-f7c3-4350-aaff-4bc22f823dd8 fwd="195.12.167.97" dyno= connect= service= status=503 bytes= protocol=https
App works when I run it in my localhost like this: npm start
2018-10-04T17:09:24.933184+00:00 app[web.1]: npm ERR! Failed at the mystery_of_dungeons#1.0.0 start script.
2018-10-04T17:09:24.921760+00:00 app[web.1]: at Function.Module._resolveFilename (module.js:542:15)
2018-10-04T17:09:24.921763+00:00 app[web.1]: at require (internal/module.js:11:18)
2018-10-04T17:09:24.921766+00:00 app[web.1]: at Module._compile (module.js:641:30)