I have a premium spotify account and have been listening in "offline" mode for over a year to all the playlists or albums I have downloaded. This morning I get on and cannot access any of them. None of them have the green arrow lit anymore and it keeps telling me to 'go online to download'. These have all been downloaded already and saved on my phone. I've done nothing different. It did ask me to log back in this morning, when I never have had to do that.
I did have to go back to online mode! The only bad thing was I had to wait until all my previously downloaded musice, re-downloaded once I was able to connect to wi-fi. So it took a while to restore all my playlists.