I tried to open the Duolingo Labs link (https://www.duolingo.com/labs) multiple times, but it kept redirecting me to my home page, my language learning tree. Not sure is it normal for some reason, or my it's just my browser...
I think it only works if your base language is English. If you are learning from a different language than English try switching to a course that you are learning from English.
It only works if your base language is English, so go to a course that you're learning from English and you should be able to access it.