The problem multiple people have had as outlined in this link -
Is still a problem and the fix has gone unanswered.
All suggested ways of fixing the problem don't work.
Every time you try to sync your playlist for "Available Offline" the slider on the iDevice toggles itself back to off and on PC when you click make "Available Offline" it says premium users only even though I only want to sync my own local files. When you go to devices on Pc and click manually sync playlists and then try to select a playlsit to sync, as soon as you click the check-box it disappears and then reappears unchecked along with all the other check boxes. The only one that stays checked is local files which is all I really want to sync, but it never starts syncing. The "local files" playlist always has pending under it. Something is obviously wrong with something. I just want to be able to sync all my local files to my phone like I used to be able to.
Also side note: I have used my Spotify free account on a PC, Android Tablet, iPhone 4S, and two iPhone 5's (One was stolen) I had my device list reset in the "reset devices" thread already. My main goal is just getting my music on my iPhone 5 that is on iOS 7 beta 6 currently, but I still had this exact same problem as far back as 6.1.4.
I seriously hope that this problem gets fixed soon. I love Spotify and would hate to just have to stop using the service since I am already so deep into it.