sm-g930t unlock server error help

Model: SM-G930T
Android version: 7.0
PDA version: G930TUVS4BRC1
CSC version: G930TTMB4BRC1
Phone version: G930TUVS4BRC1
Product code: SM-G930AZKATMB
CSC country code: USA
CSC sales code: TMB
Phone SN: R38H20BWZZF
IMEI: 357425071054660
HW version: REV0.6
RF cal date: 2016.02.16
Chip name: MSM8996
Modem board: MSM8996
Security patch: 2018-04-01
Boot Warranty bit: 0
Waiting for device to become ready... 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... OK
Rebooting to upload... OK
Searching Ramdump interface... COM3 detected
Reading data from phone... OK
Calculating... error (4)