iTunes plays song but has exclamation point in iPhone library

I open iTunes on my computer and play a song just fine. I plug in my iPhone and add the song to it, but it won't play on the phone. It shows an exclamation point on the iPhone library list viewable on iTunes. No locate option or anything when clicking on the exclamation point.

I've tried removing the song from the computer iTunes library and re-adding it. Still plays just fine on the computer. But still unable to transfer it to the iPhone.

Any suggestions?