So I upgraded to the latest update just over a week ago and noticed the supposed fix for the login issue. However, after a week at least once a day I keep getting returned to the login screen.
Solved! Go to Solution.
I also got a response from @SpotifyCares and it was helpful. However, I realized that they may have already implemented a fix for this as I was following their directions.
Try this everyone...
Login to Spotify and go here: https://www.spotify.com/us/account/set-device-password/
Note: You can also get to the above link by going to your profile in Spotify.
You'll need to use the device ID that they give you (can't figure out how to change it), and you'll need to click the button to send you an email, which gives you another link that allows you to set your device password.
Tip: save your device username in Notes on you iPhone so you can copy/paste.
Now in the Spotify app on your iPhone don't login using Facebook but login using your Spotify details (the device UID and password you set earlier).
And NOW - offline mode works as expected! I'll take this as the new way they are implementing offline mode. A bit bass-ackwards in letting us know but I'll certainly take it.
@medgirl2012 - What happens if you select 'Log in with Spotify details' (not 'Log in with Facebook') and use your FB email and password?
Of course we're looking into a more permanent solution. For now though please let me know how that work around goes.