Z3X vivo preloader port not working

[GsmRock]

hello pandora team i see a problem
plz help..

Selected model: Vivo PD2139JF (Vivo Y21A)
Operation: Erase FRP
Software version: 5.6

Host Power Off... OK
Switch virtual port to NONE... OK
Connect Type-C to HUB... OK
Host Power On... OK
Connect phone to [BOX or PC] in PRELOADER Mode
Waiting for device... OK
Driver: [MediaTek Inc.,wdm_usb,MediaTek PreLoader USB VCOM (Android),usb2ser.sys,3.0.1504.0]
Device found at COM66 [PRELOADER]
Open port... OK
Send start cmd... OK
Get HW code from device... 0766
Get sec config... OK [00000005]
Active sec flags: [SBC DAA]
Get HW & SW version from device... OK
HW VER: CA00, SW VER: 0000, HW SUB CODE: 8A00
Detect chip [MT6765]
LibUSB installed
Library Version [2]
Select platform... OK
Init BROM... OK
Force Charge... OK
Disable WatchDog Timer... OK
Reopen port for libver2... OK
Preloader exist. Skip connection verification.
Get ME ID... OK
ME_ID = 0x5E5EA9DE, 0x0F7319D2, 0x45B041F1, 0x901299A2
Load DownloadAgent... OK
Search DA... OK [2]
Send bootloader... error(DA_INIT_KEY_FAIL). Need secure DA agent with valid sign for this phone.
Advanced Authorization (Preloader) not supported for this preloader version.

vivo preloader connect show this error only