Any difference in the response headers if you refresh the page and bypass the cache via Ctrl+F5?

Creating a new profile had no effect.

Ctrl+F5 had no effect

Do you have any security software running on your Mac?

You can also check the connection settings in Firefox.

• Firefox > Preferences > Advanced > Network : Connection > Settings

See "Firefox connection settings":

• https://support.mozilla.org/kb/Firefox+cannot+load+websites+but+other+programs+can

There is no security software running and there is no proxy, firewall configurations.

Does the site work normally in Safari or Chrome?

Yes. Under safari and chrome Netflix and other sites show as normal. I deleted FF and reinstalled. Same issue.

Chrome's developer tools look a bit different, but if you use Inspect Element on the Netflix page there is a tab similar to Firefox's Network tab where you should be able to see whether Chrome is accessing the custom font file on the same path and whether it is getting the Access-Control header back from the server that Firefox is not showing.

I still can't think of any other reasons for the difference.

It should be noted that I jumped back several versions of Firefox. Trying version 40, 39 and 38. All have the same issue. I made a big jump to 25 and everything rendered properly.

Problem exists from 31-41. But prior it doesn't

Firefox Developer edition 43 works fine.