This is a new problem for me. I've been a premium user for many months and i have had nothing but a positive experience with Spotify thus far. Today, however, when i added a new playlist, it synced from my computer to my phone perfectly but then wouldn't allow me to make the playlist available offline on my phone (it is available offline on my comp). I have an iphone 5s and the most recent iOS software 7.1.2.
I added a screenshot to this post. The first track of the playlist in each case (3 different playlists) was made available offline, but the rest of the tracks weren't. I have 7GB of free space on my phone, so it can't be that.