I also get communication errors with iOS 11.1.2 and control app 2.9.4. I have tried all resets possible. After connecting via Bluetooth and starting the control app the app seems to work for some time but then the attached error message comes up. Distance between H9 and iOS device (iPhone 6 or iPad Air) max. 2 meters.

25 Nov. 2017: I have tried my old iPhone 4 with iOS 7.1.2 and H9 app version 2.9.4 – same connectivity problem. This iPhone worked fine before. I believe that something is wrong with the iOS app.