iTunes won't sync smart playlists

So I have 8 smart playlists plus 6 normal playlists in my iTunes, it's all been working well and it's been syncing all of them until about a week ago. After I synced it, I noticed that only the normal playlists were on the ipod, not the smart ones while they are still showing in itunes, I tried re-syncing but it didn't work, I still only have normal playlists.... PLEASE HELP!