Purchased songs not playing in iTunes on iMac

The song library on my iMac is hit or miss. I've reauthorized it but this hasn't fixed the problem. certain purchased songs won't play. They act like they're going to play but just go from beginning to end. I experienced the same problem on my iPhone. I fixed it by adding the song to a play list and viola, it played. Not sure if it fixed it but it played. This didn't work for the iMac. If anyone has suggestions I'm listening. Thanks and Happy New Year!

[Re-Titled by Moderator]