Can't add group to address book on device, but can do so on the simulator, why?

I have added a question to Stackoverflow about the problem I'm having here.

For some reason, the code I have posted works fine on the simulator in XCode, but fails to work on several devices I've tried. I'm wondering what the reason might be.

Another person ran into a similar problem, but with 64-bit devices, here.

I've tried running the code on an iPad 2, as well as an Ipad Air, Ipad Mini, iPhone 6, etc. All ranging within 8.2 - 8.4 for the SDK version.

Could someone explain to me why the code in my SO post simply won't work on the device?

Thank you very much in advance!