Node.js app doesnt work when deployed, but on client it does

Hi! I’ve deployed my first Node.js app to digitalocean. The problem is, on my Home-Pc the app runs perfectly, while the deployed version doesn’t. I’ve followed multiple tuts and am genuinely stuck. The stuff that doesn’t work : When I authenticate with OAuth (passport) I don’t get redirected back / hang on the redirect to the deployed server. Usually this would be a wrong redirect URI, but it works on my home pc without a problem. I copy & pasted and stared at everything over and over, but the only variable that should change from my home pc to the deployed server is the URI & it doesnt have any issues.

this is the github link https://github.com/Twiggeh/SC2Heroes

It doesn’t make sense at all. Why would a deploy & redirect break it