Hi Nancy
To help, can you try answering the following:
1. Are the files in mp4/m4v format?
2. Is the screen resolution no greater than 640x480?
3. Is the video bit rate no greater than 2.5mbps?
4. Is the audio bit rate (if variable bit rate is selected) no greater than 192 kbps?
5. Do you have sufficient space on your device?
6. Does the video play in iTunes?
Good luck.
