Problems playing downloaded music

[MrThomasson]

Hi,
I am using a OnePlus X device with Android version 5.1.1. and Oxygen Version 2.2.1-X.
I am using Spotify Premium for as long as I can remember without any problems untill a month ago.
-My downloaded songs (Green Mark is there) won't play anymore. Just one song works over the 500 I have downloaded. They used to work all before.
-Since a week even Wi-Fi streamed songs stopped working.
I haven't tried it with data because I don't have a data subscription thingy.

I tried to solve it by turning the phone off and on, signing out and in again, re-installin/updating the app and re-downloading song again. Twice.

Can anyone help me solving this problem?

-TB