Does the web page say something like "what's new with Slingplayer?" If so I have seen that disable the ability to click on watch. What you would need to do if that is the case just click on "continue" and if another pages comes up click "done." Once you click through that ad you should then be able to access the "watch" button.
If you are experiencing a different issue please post back with more information.
Hope this helps!
The Sling Moderation Team - Leanne