This issue might happen with IOS7, because your local tracks are not shared with other applications such as Spark. Message you will find then while browsing into your local track spark will be "No item found". Please follow up the below steps to solve this issue:
Go into your Iphone settings.
Select the Spark apps in the list
Two options will be available from there - tick on the option "Media Library" to allow Spark to access your locals tracks
Re-open Spark, wait until the full library is loaded
Products: Phantom | Version: 1.8.1
Setup: Solo, Duo or Multi-room | Source type: Local
Creation date: 23/09/2016 | KB article ID: SP0209