Episerver Find: Enable automatic tracking not working

Hi,

I use demo Service and i enable automatic tracking by call Track() on the search query like bellow

contentResult =
                    search.Track().GetResult(hitSpecification, filterForPublicSearch);

And then i perform search several time followed by i goto Find-> Manager->Statistics

I don't know why i can't see any Search phrase.

Can anyone tried it before please help me?

Regards,

Thang Le