Can't unlock AT&T G955U B5

is it not supported yet? or is there any other way around?

Waiting ADB device... OK
Reading phone info...
Model: SM-G955U
Android version: 8.0.0
PDA version: G955USQS5CRF5
CSC version: G955UOYN5CRF5
Phone version: G955USQS5CRF5
Product code: SM-G955UZSAATT
CSC country code: USA
CSC sales code: ATT
Phone SN: R38J3095PFR
IMEI: 35775XXXXXXXXXX
HW version: REV1.0
RF cal date: 2017.03.16
Chip name: MSM8998
Modem board: MSM8998
Security patch: 2018-07-01
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
Searching Ramdump interface... COM4 detected
Reading data from phone... OK
Calculating... error (0)