If the phone software upgrade stopped before completion, please don't close the update tool and try to update again following original instructions.
If you closed the update tool already and the phone will not turn on normally, please follow the below steps.
1. Remove back cover and battery.
2. Record IMEI/ESN/MEID from device label in battery well.
3. Replace battery and back cover.
4. Connect the device to PC via USB Cable.
5. From the help menu, select Options > Upgrade Recovery.
6. Input the Model name and Serial or IMEI/ESN/MEID and press OK.
7. After checking the phone information, it will start to update automatically.