Why can't I watch videos on my Firefox? It tells me I need Flash player.
Like any other browser, Firefox strongly depends on Adobe Flash Player to display a lot of animation, video, embedded audio, game and other content. You need this plug-in/component installed to to be able to watch videos.
There may be some error on your existing flash software/ add on for the Firefox. Try to install one of the available flash player based on your requirement.
Good Luck :)