Microsoft Lumia 640
T-Moblie
Unlimited data
Spotify Premium

For whatever reason, Spotify refuses to allow me to use it on a mobile network.  I see no settings to change this.  Under "Settings -> Offline & Sync" it identifies my connection type as "WiFi" and will not change to mobile data, just say "Spotify is offline" and "Spotify cannot be reached on this connection".

What am I missing here?  I have no problem streaming anything else (iHeartRadio, if it *ever* works, Xbox Music, Xbox Music Radio, TuneInRadio, MixRadio) except this app - which *should* also be covered by T-Mobile's music freedom.  What's going on here?  Getting annoying as I primarily use Spotify in the car.