I am having the same issue with my kids' Kindle Fire devices. I updated their privacy settings to allow them to play multiplayer games and now the app crashes every time on startup. However, I cannot find this XBLStorage.json file. Where is it? How do I locate it?
I would also like to add... How can you possibly have failed to fix this issue after all this time? This is a serious user experience defect. It has been years since it was reported. I notice the most recent urgent defects that were fixed included such pressing problems as not being able to place a lantern under the stairs and a player's shadow disappearing when they are crouching and creeping. Surely the total inability to even start up your application after making common and every day updates to security settings merit the same level of attention and urgency as those very important issues?