.mp4 movie files from UTube do not play on IPAD 2
I am a noob here regarding the iPAD.
I downloaded a youtube 720p video to a mp4 file on my PC. It plays fine. I uploaded the file to dropbox and then was able to play it fine through Dropbox on my iPAD 2. With the confirmation ... I starred the file to make it accessible locally. Then clicked on it again to play it. No juice. It will not play.
What gives ? My understanding was that in Dropbox for iPad when you star a file it is accessible offline. Moreover, if it played before I starred it ... why not after I star it ?