Wiktionary is really not a reliable dictionary, it's full of mistakes, but if you want to use it being aware of that, this addon is not working for me, clicking the addon button fails to bring the addon window with the result. It's the reason why I give only one star, it doesn't work at all for me.
You need Firefox version 57 or better. Which ff version are you using?
Or, if you've changed the wiktionary url in the preferences, then make sure that your url has no typos and is exactly like the examples, i.e. "fr.wiktionary.org" and not "fr.wiktionary".
As for Wiktionary, it's community driven and not-for-profit (r-right?). I like that.
