error unlocking g920f

i cant unlock a samsung s6 i keep getting an error

Checking Login and Password... OK
Ballance: 10 crd.
You have 10 credit(s) left. This operation takes 2 credits.Continue? Yes
Waiting ADB device... OK
Reading phone info...
Model: SM-G920F
Android version: 7.0
PDA version: G920FXXU6ERF5
CSC version: G920FBTU6ERG1
Phone version: G920FXXU6ERF6
Product code: SM-G920FZDAEVR
CSC country code: UK & IRE
CSC sales code: BTU
Phone SN: RF8HB1HF0JV
IMEI: 353560083317616
HW version: MP 1.00V
RF cal date: 20161114
Chip name: EXYNOS7420
Modem board: SHANNON333
Security patch: 2018-06-01
Boot Warranty bit: 0
Searching server... OK
Checking server answer... modem required
Rebooting phone... OK
Waiting ADB device... OK
Initialization zTool... OK
Running zTool, please wait...
Start... OK
Initialization... OK
Generate and check client proof... OK
Verify proof by client... OK
Reading data from phone... error (1)

Done with Samsung Tool PRO v.33.5