We've had a number of users tell us that OnSong will begin to start and then shutdown to the home screen when no Internet connection is available. We have confirmed this a bug in iOS 9 on iPads, potentially only those with cellular data. iPhone models do not appear to be effected. The crash is caused when OnSong attempts to find nearby peers via OnCue using the original version of OnCue which triggers an exception in iOS 9's networking libraries.
New installations of OnSong will automatically select the new version OnCue and not the original. The original version of OnCue uses an Apple framework that has been deprecated by Apple since iOS 7, but remains available in OnSong for backwards compatibility with iOS 5 and iOS 6 devices. Until iOS 8.4, this framework has continued to work. Current versions of iOS have caused bugs in the framework that will likely not be fixed by Apple due to their deprecated status. If you had this version of OnCue set in your preferences, it will continue to be used in iOS 9 which is what is causing the issue.
Luckily the fix appears to be simple. Go into the Settings app from your device's home screen and choose OnSong on the left. Scroll to the Menu Settings section on the right and open the Sharing option. Under the OnCue section, change OnCue Version to "New" instead of "Original". Close out of the settings screen and open OnSong.
We have changed OnSong 1.999 to automatically switch to the new version of OnCue if it was already set. We are planning allow an override of this in case Apple fixes this bug in the future.
We are working hard to finalize OnSong 1.999 to correct this an other found issues. We thank you for your patience as we work to ensure stability on the best app for musicians!