Threaded Comments Not Working. How Can I Fix This?

I just installed Comments Plus and someone left a comment at http://xokenglish.com.br/xok/debaixo-do-pe-de-manga-onde-a-xokenglish-comecou/

I would like to reply to their comment...but when I click reply nothing happens.

Does Comments Plus support threaded commenting? If so, how can I activate it.

Thank you in advance.