My iPhone 5 will not download "recently purchased" to phone. The box is checked. Songs are on phone just not assigned to playlist

My iPhone 5 will not download "recently purchased" to phone. The box is checked. Songs are on phone just not assigned to playlist. When I hit sync the available space goes from 13 free GB to 8 free GB. When it get to end of sync it says waiting for changes then goes back to 13 free GB and nothing changes. Any ideas