iPhone 6 disappears as Roon endpoint when lockscreen activates

I’m told that others are able to have Roon Remote zone work on iPhone when lock screen activates but on my iPhone 6 plus I can’t get that to work. Experiencing the following symptoms

Behavior looking at status from Windows 10 Roon core server playing to Roon Remote zone running on iPhone 6 plus, Sprint carrier. When zone disappears, music stops

  1. iPhone disappears as a zone when screen lock timer kicks in
  2. iPhone disappears as a zone when screen lock button is pressed on right side
  3. iPhone reappears as a zone when phone is unlocked after pressing home button
  4. iPhone disappears as a zone when any other application is the foreground active application

iPhone zone is not set to private. Overall this sounds like Roon is going into a “suspend” mode whenever the screen locks or another app is in the foreground… I don’t see any option to change this behavior. Any thoughts on how to fix?