So... I've noticed this is an on going problem! It really shouldn't be.
I've been trying to sync local files from my desktop service to my Iphone 5.
I've tried with the cable, without.
I've tried logging in and out, on both devices.
I've tried restarting the devices.
Restarting Spotify, on both devices.
They are both connected to the same wifi.... I don't know my neighbours passwords so I wouldn't be connected anywhere else.
It's been well over an hour of restarting and resetting. I'm sick of this happening whenever I try to sync my own music. I will be leaving the service if this cannot be fixed.
This is an ongoing problem for at TWO YEARS now. It's not just been me that suffers with it.
Perhaps if Spotify stopped messing with design and fixed their buggy software, this wouldn't be happening.