7715 sp unlock fail.

Action : SP Unlock
Boot : SC7715-EMMC
Tips:
1.Remove Battery, Insert usb cable, Insert battery
2.power off Phone, Remove & Reinsert Battery , insert USB Cable
(bootkey’s Volume Down or volume up)
Waiting for Phone Usb….
Phone found : SCI USB2Serial (COM12)
Connecting…
Bootstrap: SPRD3
Connected done.
sending 1st boot…
1st boot done.
Sending 2nd boot…
2nd boot done.
Checking H/W report info…
Read info is done.
Loading CST Boot image to RAM…
Error: 0xe8 [not respond].

Checking sp lock info …

Items found.
Error: Lock is not set or unsupport.

Action completed
Time taken : 00:00:42
Reconnect Battery/USB Cable
CS-Tool Ver 1.37.03