firebase hosted react app returns "you need to enable JavaScript to run this app"

I have a web app made with react which is hosted via firebase hosting, and a backend server using express hosted on cloud functions.

Website: https://studyi.co/

The landing, login and signup pages work as expected, but on any route with /app/{route} (e.g /app/dashboard), a blank page is returned and the request returns "you need to enable javascript to run this app"

Everything here works on dev server, where the react website was started with npm start, and communicating to cloud functions by firebase.

Any idea why?

I am new to web development, let me know if I can provide anything else.