First of all, make sure the file does have a video (some songs simply don't!)
Then, make sure the name of the video in the text file is the same as the name of the video. For example if in the txt file you see:
#VIDEO:Davichi - Secret.mp4
Then make sure the video is titled "Davichi - Secret" (and is in mp4). If it is called "Davichi-Secret" the game won't accept it.