Heroku error code=H10; desc="App crashed", dyno= connect= service= status=503 + Python Flask code + Free Dyno

I wrote a Hello-World program. -_-

You can find the code here: https://github.com/sahaanirbannew/identify-bird-name-from-text

This is the code on app.py:

from flask import Flask, request, render_template
ON_HEROKU = os.environ.get('ON_HEROKU')

@app.route('/') 
def hello_world():
  return "Hello World"

if __name__ == '__main__':
    app.config['JSONIFY_PRETTYPRINT_REGULAR'] = False
    
    if ON_HEROKU:
      port = int(os.environ.get('PORT', 5000))  # as per OP comments default is 17995 
    else:
      #port = 3000
      port = 8080
    app.run(debug=True, port = port)

This is the requirements.txt

flask
gunicorn

This is the Procfile

web: python app.py 
web: gunicorn app:app

This is the error:

2022-09-25T02:51:25.386162+00:00 heroku[router]: at=error code=H10 desc="App crashed" method=GET path="/favicon.ico" host=bird-name-ner-wrapper.herokuapp.com request_id=8475677a-5136-4329-a0a7-11f12b1728ab fwd="49.37.34.218" dyno= connect= service= status=503 bytes= protocol=https

**What am I doing wrong? ** I feel incredibly stupid.