I would not use Kingroot!
Use this instead:
Please look in Z2 forums here on XDA as well next time.
- Make sure device is connected
- Make sure USB-debugging is enabled
- Make sure no Sony PC Companion or other Sony software is running
- Make sure you have adb drivers installed (Example)
- Make sure the computer is permanently authorized for connection on the phone (you get a dialog the first time you connect)
Did you use the SuperSU from market? Because it's a known issue this SuperSU can not update binary. Use latest one from here: http://download.chainfire.eu/447/SuperSU/UPDATE-SuperSU-v1.99r4.zip