Nike Running + Spotify don't work on my iPhone 4s

[martech]

I'm a premium subscriber and I use spotify offline mode when I go out for a run. When I begin my run under the wifi network the music starts but later -after a couple of minutes- stops. I have to stop my run, open spotify, and click play or next song for the player to start playing again.  Sometimes this works, sometimes it doesn't.  If Ibegin my run out of the wifi network no music will be listened.... 

iPhone 4s

iOS: 9.0.2 (but this happened too with iOS 😎

Spotify: 4.1.0

I have already done the uninstal and the re-instal process of BOTH apps (Spotify and Nike Running)

I have already done teh 10 sec pressing both iPhone buttons.

What else should I do to fix this? Any idea? Its quite annoying!!!!!