Files won't sync to iphone 5s

[rewind3487]

I enjoy spotify for alot of reasons but I'm looking to download all of my music to my iphone so that I don't eat up as much data. I have "songs" and all of my playlists set to "available offline" but it shows its not syncing them anymore. A few songs downloaded and I see a mix in my "songs" of ones with a green arrow, ones with a grey arrow, and ones with no arrow next to them. Connected to WiFi with 35GB remaining of space and I'm still not able to get the sync to resume. It's spotty and I never know why it works when it is working. 

Thoughts?

[user-removed · Accepted solution]

So Spotify has a 10,000 offline song limit per Premium account spread across 3 devices.

That means each device can have 3,333 songs saved for offline access. Maybe you've reached this limit? If you have ~15 GB synced music that would probably explain it.