Some are saying that the feature does not work for them. It shows up and disappears after they click on the option. I cannot replicate it but there is a vast number of complaints in the Google Web Search Help forum.
The complaints say it mostly happens in Chrome, but I tested it in Chrome and it works - and I bet you Google tested it in Chrome as well.
Despite that, yesterday, a Google representative said:
Hi all, thanks for the updated info. I'm going to investigate this, and may get back to you with some more questions. Stay tuned.
Do you have this issue?
Forum discussion at Google Web Search Help.