VTR-L29 imei reapir problem
 

Before operation turn phone to TestPoint mode:
Turn off phone, then short TestPoint on phone pcb
and plug USB cable
Wait for device "HUAWEI USB COM 1.0" in Ports


Repair
New IMEI 1 : 354068040935867
Unlock downgrade/customization limitations
Reboot after repair
Selected Cpu/Bootloader - Kirin960_Hi3660_T0_A8.0_V5
2021-11-16 13:18:01.815 Connecting to server...
2021-11-16 13:18:02.018 Connected!
2021-11-16 13:18:02.737 Find device COM26, handle 11040
BOOTLOADER selected to update:Kirin960_Hi3660_T0_A8.0_V5
2021-11-16 13:18:03.127 Downloading bootloader...
FILE TO download: Kirin960_Hi3660_T0_A8.0_V5_3.dtwork
downloading file Kirin960_Hi3660_T0_A8.0_V5_3.dtwork...
2021-11-16 13:18:05.659 Success
FILE TO download: Kirin960_Hi3660_T0_A8.0_V5_4.dtwork
downloading file Kirin960_Hi3660_T0_A8.0_V5_4.dtwork...
2021-11-16 13:18:06.831 Success
FILE TO download: Kirin960_Hi3660_T0_A8.0_V5_5.dtwork
downloading file Kirin960_Hi3660_T0_A8.0_V5_5.dtwork...
2021-11-16 13:19:32.426 Success
2021-11-16 13:19:32.447 Bootloader write success!
2021-11-16 13:19:32.450 Waiting for device REMOVAL/INSERTION...
2021-11-16 13:19:39.295 Device ready!
2021-11-16 13:19:39.423 Reading info...
2021-11-16 13:20:07.509 Read signed IMEI FAIL!
2021-11-16 13:20:12.637 Read NV FAIL!
2021-11-16 13:20:12.762 Read oeminfo FAIL!
2021-11-16 13:20:12.762 Phone not found !

Fastboot provided info:
CPU: hi3660
Model: VTR-L09
Firmware: VTR-L09 9.1.0.252(C432E1R1P9)
Vendor: hw
Country: eu
MEID: 86554503482030
SN: 6PQ0217A31004570
PCB SN: 024ATC17AV003276
WIFI MAC: 940E6B402BB7
BT MAC: 940E6B403068
Theme color: black
Device color: tarnish
FBLOCK: 1
Bootloader FB lock: unlocked
Bootloader User lock: locked
2021-11-16 13:20:13.028 Phone not found !
Memo log saved to H:\GSM PROGRAMLAR\HCU_358\Logs\20211116_132013_HCU_Xloade rRepair_554D6DDF5242804.txt

On this page: https://www.dc-unlocker.com/firmware-catalog enter in the search field "960", you should see files: Kirin960_NV_Partitions_v1_L09.dgtks" you should try to reflash your phone with it, and then repeat IMEI repair.