In short,

I've got 2 ipads, 2 iphones, I'm a premium spotify subscriber, I can use the native apple Remote app to stream music from either ios device to either my laptop or to my Denon 3312 Amplifier (which supports Airplay) via Airplay.

However, I have not once seen the Airplay icon from any ios device using the spotify app. I've tried turning all of the apple devices off but one to elimiante interference.

I've shut everything down multiple times and upgraded all software to the latest version.

What's really annoying is that it works perfecty via the native iphone Remote app.

Any suggestions would be very grateful.