Close SOC on your PC.
Reboot your phone.
Connect the USB cable from phone to PC.
On the phone, turn on USB-debugging. If it is already on, turn it off and back on again.
Start SOC and try to unroot. Done....hopefully.
As you can see above...I found it worked most often when I toggeld the USB-debugging at least once after the phone booted. Just "leaving USB-debugging on" seldom worked for me.