HELP! All tracks downloaded for offline listening have been deleted

[Gioghi78]

I sync my iPhone with iTunes to back up and sync photos, music, ... when finished, I realized that all the songs downloaded from spotify for listening offline are no longer present. Specify that the playlists are there, but the green triangle is gone. A huge thanks to those who explained to me the reason so as not to repeat in the future.

Use the version ios7 and I've already tried logout and login

[Peter__]

Strange, backing up shouldn't remove offline content unless it decided to clear application caches too. Did it do any software updates whilst the phone was connected?