I don't have a very large amount of 3G network usage in my plan with Verizon so I try to stay offline on my spotify account so I don't use any internet when I'm not on wifi however many of my songs will not play offline and they all turn to a dark gray shade and when I click on one a pop up saying " this song is not available offline. do you want to go back online? " . I have everyone one of my songs downloaded with the little green arrow next to it and everything but when I'm not connected to Internet the song titles turn gray and this is very frustrating because I cant listen to the music I want to in the car or when im not at home connected to Internet . i am a premium user of about 3 months and this has been a problem I've had for about 2 weeks . what's going on ???
What version of the SPotify app do you have installed? Can you check for updates in the Play Store?
I also wonder if your cache has become corrupted somehow; Please read the guide linked below for details on the most common issues and how to fix them. Usually a clean install is the first step to take and resolves most of the usual issues; the guide details the steps to take to ensure a full 'clean installation' is achieved - This includes checking redundant folders and a REBOOT!