Needs MathJax 2, not the 3 that it grabs from the git clone

[AzzieDev]

As soon as I cloned the current version of MathJax 2.7.9 which was released on August 25th, 2020, everything worked properly.

https://github.com/mathjax/MathJax/releases/tag/2.7.9

Download, extract to the "thirdparty" directory, rename the directory you extracted to just "MathJax" and not with the version number.