iPhone, switch from streaming radio subscription without losing sound?

I stream broadcasts from BlazeTV to my iPhone (SE), during witch I used to be able to switch to another program, (e.g. mail, games or whatnot), the app would come up and the sound from streaming would continue. Now when I attempt this the sound quits. I don't know what I've done. I've examined all settings and so forth but can't figure out how to remedy the situation