It actually does work, but not very reliably. Most of the times all I can see is a blank page with no text. But if combined with some other web-based dictionaries (Wikia in my case) in the same group, then from time to time I do see the definitions
I've seen this pattern in the past as well. Some web sites work just fine and some others are empty unless there are some other web dictionaries are enabled on the same group (and the result varies, with some additional web dictionaries everything works, with some other still only empty pages).