Drk repair fail j710gn

Operation: Repair DRK
Selected model: SM-J710GN
Software version: 33.7

Checking local file... OK
Searching server... OK
Compare local and server file... OK (up to date)
Searching USB Flash interface... COM39 detected
Setup connection... OK
Reading data from phone... OK
Sending data to phone... OK
Sending data to phone... OK
Waiting ADB device... OK
Reading phone info...
Recovery build version: 6.0.1
Boot version: J710GNDXU1APG1
Platform: exynos7420
Boot serial: 52039e1df092939f
Product board: j7xelte
Initialization zTool... OK
Running zTool, please wait...
Start... OK
Initialization... OK
Generate and check client proof... OK
Verify proof by client... OK
Checking DRK status... NG!
Writing DRK... error ()
Done with Samsung Tool PRO v.33.7