I'm maintaining an app which is mainly targeting old devices (iOS 9) audience. In its latest version, I added some nice changes that I always tested successfully on my old iOS 9 device. It always run fine (debug mode connected to Xcode). However, after releasing the app through the App Store, the app crashes immediately at launch on all iOS 9 devices (mine and customer' devices). I later discovered the capacity to generate IPA file on Xcode and install them directly on the iOS 9 device. I hoped with that method to debug my app quickly without having to debug blindly by releasing several small changes on each App Store version until I understand the changes which makes the whole app crash. However, when using this IPA methods (which shall produces a similar app that what the App Store generates), the app does NOT crash.. I am now a little bit lost.. I have to revert all my code back to the previous stable state without having any clues which code is killing my app on start. I even reverted already all the AppDelegate and Main ViewController changes... without success... it is still crashing through the App Store. Any Idea / Suggestion on how to make a step forward? Is that normal that generating an IPA file in Xcode is not the same that releasing the app through the App Store? FYI: The app releases on App Store crashes on iOS 9 but no on newer iOS... Thank you!