Use a local copy of MathJax with Doxygen
When MathJax is enabled you need to specify the location relative to the HTML output directory using the MATHJAX_RELPATH option. The destination directory should contain the MathJax.js script. For instance, if the mathjax directory is located at the same level as the HTML output directory, then MATHJAX_RELPATH should be ../mathjax. The default value points to the MathJax Content Delivery Network so you can quickly see the result without installing MathJax. However, it is strongly recommended to install a local copy of MathJax from https://www.mathjax.org before deployment.