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.
