My ripped .mp4 movies will play in QuickTime and AppleTV 3; but not in iTunes? Anyone else have this problem?

I used Make MKV and Handbrake to rip 2 purchased DVDs to mp4. Both will play on my AppleTV 3 and in QuickTime. But in iTunes I can only can see a still-frame, and use the slider to fast-forward and rewind them. They won't play.

If iTunes incorporates QuickTime into playback, I don't understand, as I can play them in QuickTime. I really didn't understand after I watched one of them on my AppleTV 3.

Anyone else having this problem?