Accessing file via URL

Question

I deployed a python flask app on Heroku and it works fine. I have also uploaded a well-known folder that contains an apple-app-site association file, but when I try to access the file via URL, it returns 404. Basically, I'm testing universal links, so I wanted the apple-app-site association to be accessible. When I checked the status in the branch.io aasa validator, it returns server error, please find attached the screenshot Screenshot

What I'm doing wrong?

main.py

from flask import Flask
app = Flask(__name__, static_url_path='/well-known')
@app.route('/')
def index():
    return "<h1>Welcome to Universal Link - iOS<h1>"

wsgi.py

from app.main import app
if __name__ == "__main__":
  app.run()