Thank you for posting in the Slingbox answers forum! I'm sorry to hear you are unable to get a video Signal when trying to Watch live TV from your television.
I have an idea of what could be causing this. If you go to newwatch.slingbox.com and hit settings above the video player, click on configure inputs. After you do this, check and see if you are configured to HDMI or Component. You most likely have the component input configured. If it is, you will not get video on the TV because the TV is using HDMI. Therefore you will need to switch the input over to component.
Feel free to reply if this does not work for you.
Hope this helps!
The Sling Moderation Team