A couple of months ago Square Enix pulled The World Ends With You from Apple's App Store due to imcompatibility with iOS 8 and many believed this was the end of the Solo Remix since the company issued a statement that it probably won't receive a fix. The game also broke on Android 5 but remained on the Google Play Store.
But rejoice, I just received a notification that Square Enix has brought the game back to the App Store with iOS 8 support and also updated the Android port with Android 5 support.
Source: My phone