Submission is not working even if it is correct

Tell us what’s happening:

Your project link(s)

solution: https://boilerplate-express-2.faatehsultan.repl.co

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.150 Safari/537.36.

Challenge: Serve Static Assets

Link to the challenge: