M4V wont sync with my ipod

a few months ago, I made a video in iMovie 9.0.4 then i converted it to an M4V file so i could use it on my ipod touch. when I tried to sync it to my ipod, itunes rejected it in the sync. last month, I got a nexus 7. as a test, I loaded my movie to it, and was able to play it back just fine. why won't itunes allow it to be installed on my ipod?