Purchased playlist on iPhone 5 not updating

Hi,

I am having a problem which is getting very frustrating. I am using an iPhone 5 with iOS 6.0.1 with the latest version of iTunes.

The problem I am having is, in the past, if I purchased a song on my iPhone, it would appear in my purchased playlist on my iPhone as well as my Mac.

However, if I purchase a song on the iPhone, it is playable via Artist/Songs/Albums on my iPhone, but it won't show in the purchased playlist. (It used to automaticly update)

I use this playlist everyday in my car, and new songs never appear.

I hope I am not missing something completly obvious here, but I have google'd myself to death 😉.

Let me know if you need any more information.