Note 4 N910U 5.1.1 cant unlock,read and write cert

i cant read,write cert and unlock this note 4 Lollipop.
I tried all roms from samsung tool but i couldnt install using odin. shows FAIL

"Running zTool, please wait… error" from latest samsung tool.

do i need to downgrade to unlock this phone? I cant find any tutorial to downgrade from 5.1.1. I tried stock rom from sammobile and z3x download too didnt work.
Need help thanks ( also updated to 24.3 just now and similar result)

Operation: Read CERT
Selected model: SM-N910U
Selected port: COM4 USB Serial Port
Software version: 24.2

Waiting ADB device… OK
Reading phone info…
Model: SM-N910U
Android version: 5.1.1
Product code: SM-N910UZKEVFJ
Phone version: N910UXXU1COL1
PDA version: N910UXXU2COL2
CSC version: N910UVFJ2COL1
CSC country code: Fiji
CSC sales code: VFJ
HW version: MP 0.600
Modem board: XMM7260
RF cal date: 2014.10.10
Checking Super user right… true
Reading nv data… OK
Checking magic… OK
Running zTool, please wait… error

Done with Samsung Tool PRO v.24.2