I am trying to upgrade my S4 to the latest firmware version. I've tried trough the telephone (with Wifi) but in the very end of the process it says there is an error and it suggests me to connect the device to a computer and to try out with Kies. I only own a macbook pro so I've downloaded the Kies version for Mac. The point is that when I connect my phone everything is fine until I press the button that starts the upgrade. At this moment it seems I loose the connection between Mac-S4. I don't really know what to do. I've restarted both mac/s4 and I've even uninstalled and reinstalled Kies but the issue remains.