ZTE Z755 cannot unlock by sigmakey

SigmaKey 2.21.01 Qcom: Direct unlock
ZTE Handset Diagnostic Interface (COM17), Provider: ZTE Corporation, Driver ver.: 1.2066.1.3, Date: 4/28/2010, USB\VID_19D2&PID_0500&REV_0228&MI_00
Version: P821A21_CRICKETV1.0.0B17,
Firmware: MPSS.TR.2.0.c15-00029-M8610BAAAANAZM-1.15331.3
Date: May 9 2016 10:53:50, Mar 08 2015 14:00:00, BAAAANAZ
Software IMEI: 866672023683641
Bluetooth address: 000000000000
Unsupported phone model