I have a 60gb video ipod 5th generation...

I have a 60gb video ipod 5th generation that i have not used in years. I updated it and cleared it of all old music and videos.. I went to my purchase history and re-downloaded some tvs shows i purchased..when i went to synic them to my ipod it said cannot be played on this ipod. Is this not working because my ipod is old or do i need to update it some how...any help would be great...thank you