I realize that this is the wrong forum and not a FreePBX problem but I figured the experts here would be most familiar with ZoIPEr app.
On my iphone, the zoiper app only rings when called IF the app is currently open when the call comes in. Otherwise it displays a banner saying missed call but no ring. I have the same problem with my MagicJack app.
Any ideas? Already tried tweaking the iphone app notification settings
Got it working. Inside the zoiper app --> settings --> incoming calls
Theres a setting, “force background” it says warning: will significantly reduce battery life, but when enabled, it works and rings the phone even when phone is locked.