samsung n910u can not write cert always fail

Hi team plz check and tell me what going on why i get this error

Code:

[Read/Write certificate started]

Gathering phone info...
Collecting information. Be patient! Do NOT disconnect the phone!
Model: SM-N910U
Sales Code: NZC
Country Code: New Zealand
Timezone: Pacific/Auckland
Android Version: 5.1.1 [LMY47X]
Build Date: Tue Dec 15 13:47:04 KST 2015
PDA Version: N910UXXU2COL2 [december 2015, rev2]
Phone Version: N910UXXU1COL1 [december 2015, rev1]
CSC Version: N910UNZC2COL1 [december 2015, rev1]
Product Code: SM-N910UZKENZC
HIDSw Version: N910UXXU2COL2/N910UNZC2COL1/N910UXXU1COL1/N910UXXU2COL2
Board Platform: EXYNOS5
Modem Platform: XMM7260
Serial Number: R28G60HPRPE
Imei: 3567720++++++++
Unique Number: CR2004421570012
Connections: AT,MTP
Battery Status: 3.68V (29%)
Network Type: GSM
SIM Status: READY
Knox Version: 0
Warranty Bit: 1
Security Patch: 2015-12-01

Determining secure image format.
done.

Creating backup.
done.

Gathering cert informations
done.

Calculating key.
Chtool app run failed!
Finished at local time: [06.17.16 11:45:23]
WorkID: 11499290