What is the extension of the video file? Downloaded Youtube files usually have .FLV. Fuze+ can’t play these (only .MP4 ).
Requirements for video files can be found here: http://forums.sandisk.com/t5/Sansa-Fuze/Fuze-Video-Requirements/m-p/187774#M70
Usually the file must be run through a conversion program. The only free one I know of comes bundled with unwanted (possibly obnoxious) software, so I won’t recommend it.
