A510F write cert error

I can read cert, read efs, write efs but can not write cert.

Operation: Write CERT
Selected model: SM-A510F
Software version: 26.2

Waiting ADB device… OK
Reading phone info…
Model: SM-A510F
Android version: 5.1.1
Product code:
Phone version:
PDA version: A510FXXU2APC4
CSC version: A510FOXX2APC1
CSC country code:
CSC sales code:
HW version:
Phone S/N: R58H70FKR1Z
Modem board:
RF cal date:
Checking Super user right… true
Initializating zTool… OK
Running zTool, please wait…
Start… OK
Init… OK
Generate and check client proof… OK
Verify proof by client… OK
Reading data… error (8)

Done with Samsung Tool PRO v.26.2

any advice please?