HDTV detected on my Macbook but the display doesn't appear.

Hello there!

My Macbook is OS X Yosemite and Macbook Air is OS X Mavericks. And I just buy new mini display port to hdmi cable, while I was trying to connect on my Macbook Pro and Air it is detected but the display does not appear to my HDTV. My HDTV is Samsung LCD, I had already plug-unplug but still did not work at all. Can anyone solve my problem here?