I've given up with Spotify and this issue. 3 different android phones, different networks both wireless and mobile and still says offline. Joined Google play music and it's been fine for over a year now. Spotify just keep telling you to do the save steps which never work. I don't know how they are getting away with this tbh... Money to Spotify is money down the drain for offline listening. Never coming back.
LOL, that's not helpful.. anyway, I finally cancelled my premium subscription to Spotify. After 10 years with Spotify, I'm gonna try some of the other services for a while. I haven't been crazy about the direction Spotify has gone over the years.. it's not special anymore.
Good to see that for 7 years people have had this issue and apparently there isnt a solution beyond "are you really online?" even if pretty much every other app works fine with WiFi and data connections .