Ipod classic will not sync TV shows and Movies that it previously had on it.

I am attempting to put some TV shows, movies, and podcasts onto my Ipod Classic. THese are movies that previously were on this devise. In Itunes, I click to add the videos, and the bar at the bottom gets bigger showing more data to transfer. I try to Sync. It goes through the sync process very quickly, and then the bar gets smaller, it says sync complete, and nothing transfers onto the device.