Posted this reply in another thread, but will repost here.

Codeforces uses the Mathjax library to format mathematical equations, and if you view network traffic on your browser, you will see that when trying to get the Mathjax library it is not getting anything back :(. So mathjax library is not being loaded.

Also, I have found a fix. Visit https:// cdn-mathjax dot codeforces dot com/MathJax.js?config=TeX-AMS_HTML-full and then reload your codeforces tab and it should fix it, it worked for me.