Please, make sure that supplied URL, actually, has any embedded Flash resources.
It may happen that the main page (index.html) doesn’t have any Flash animation, and has still images instead. However, the other pages that can be accessed from the main page by clicking links can have ones. For instance, “http://some_web_address.com” may not contain SWF/FLV files, but “http://some_web_address.com/swf.html” has the ones.
One of the simplest ways to check whether the loaded page has embedded Flash animation is right-clicking Flash animation on the page and checking if the last menu option is “About Adobe Flash Player”.
Alternatively, you can check the HTML code of the loaded page on SWF/FLV file extension occurrence.