MBP to HDMI audio problem

I was told by apple that based on my current MBP and what i needed I bought the Kanex mini DP to HDMI with audio support. I brought it home and plugged it in and there is no audio coming from the TV, and under sound in the system preferences, the TV is not listed as a sound input or output. So i looked up the dates of when the DP started supporting sound for the mini DP and a news article was marked "April 13th". I bought my model April 10th, does this mean I can't support sound out of my mini DP?

Thanks