This addon exists within FFZ and just works! It just needs to be enabled in the addon tab.

If you you the browser addon separately from FFZ it doesn't work.

awesome extension

Excellent app that lets you see pronouns in Twitch chat! IF YOU ARE HAVING TROUBLE WITH THE APP WORKING, UNINSTALL FRANKERFACE! IT INTERFERES DIRECTLY WITH THIS ADDON! Only just figured that out myself now and I'm big mad about it lol.

the extension has been fixed! if you are still not seeing the pronouns show up in twitch, please Remove the addon, then Add to Firefox again, and restart your browser :D
(unless you also use FFZ, which has a clash at the moment, but you can make the pronouns show up inside FFZ by going to the FFZ settings, search for 'pronouns')