Deploying an app

I’ve deployed my code using Heroku and it says that my deployment was succesful. However, when I try to access the website, it says there is an “Application Error”.
I’m trying to complete a QA challenge and that’s my only complication so far.

User Agent is: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.77 Safari/537.36

Challenge: Learn How JavaScript Assertions Work

Link to the challenge:

You should post your code on something like GitHub and a link to your Heroku site. Otherwise, we have no chance of helping at all.