<p>Here's one possible cause of the problem.</p>

<p>MathJax.org have paid to host a <a href="https://en.wikipedia.org/wiki/Content_delivery_network" rel="nofollow noreferrer">content delivery network</a> (CDN) to make it easier for people to host MathJax pages (at cdn.mathjax.org). However, cloudflare have increased the cost of doing this to them and MathJax have decided to focus their resources on development.</p>

<p>Consequently, as recommended by MathJax and as described in <a href="https://math.meta.stackexchange.com/questions/26166/should-math-se-support-mathjax-on-its-own-server">this math.SE meta post</a>, the hosting of math.SE's MathJax libraries have moved 
to cdnjs.cloudflare.com (which cdnjs pay cloudflare for)</p>

<p>If for any reason you're blocking cdnjs.cloudflare.com (or likely cloudflare.com more broadly) then MathJax might stop working for you on math or here on CV (along with <a href="https://meta.stackexchange.com/questions/216606/which-stack-exchange-sites-use-mathjax">other SE sites</a> that use MathJax). </p>

<p>If you're using NoScript (for example), blocking cloudflare.com would be the default action. There's some advice in the comments at the linked math.SE page about how to enable MathJax without whitelisting the whole of cdnjs.cloudflare.com :</p>

<blockquote>
  <p>For NoScript, I find that one can whitelist <a href="https://cdnjs.cloudflare.com" rel="nofollow noreferrer">https://cdnjs.cloudflare.com</a> and add an ABE rule Site <a href="https://cdnjs.cloudflare.com/ajax/libs/mathjax/" rel="nofollow noreferrer">https://cdnjs.cloudflare.com/ajax/libs/mathjax/</a>* Anonymize Site cdnjs.cloudflare.com Deny (with line breaks before uppercase letters)</p>
</blockquote>

<p>There's also advice for users of UBlock Origin and other discussion you may care to read there.</p>

<p>If you are using NoScript you could check if this is the issue by <em>temporarily enabling</em> cloudflare.com (it should show up in the list if you check the NoScript menu while reading this page - hover over the NoScript icon in your browser, which is a bold S with a small red circle and diagonal line) and seeing if the mathematics renders (you can then disable again the same way, and try to implement the safer-in-the-long-term advice in the comments at the math.SE post).  </p>
