xt1541 Unlocking phone.......Error writing to serial port ?

SigmaKey 2.33.07b1 Qcom: Direct unlock
Motorola USB Networking Driver #16, IP: 192.168.137.1
Firmware: MPSS.DPM.2.0.2.c1.8-00044-M8936FAAAANUZM-1
Date: Jan 12 2016 03:09:45, Nov 22 2015 23:00:00, EAAAANVZ
Software IMEI: 355489064295380
Bluetooth address: 000000000000
Unlocking phone.......Error writing to serial port