Do you put the board in force recovery mode before flash?
I found there is an error about ECID.
17:52:01.934 - info: NV_L4T_FLASH_TX2_WITH_OS_IMAGE_COMP@JETSON_TX2_TARGETS: *** Checking target board connection ... 1 connections found.
17:52:07.039 - error: NV_L4T_FLASH_TX2_WITH_OS_IMAGE_COMP@JETSON_TX2_TARGETS: *** Reading ECID ... SDKM_INSTALL_ERROR *** Error: ECID read failed.
Please check if the following thread could help.
Unable to flash Xavier AGX with SDK because of *** Reading ECID … *** Error: ECID read failed - Jetson & Embedded Systems / Jetson AGX Xavier - NVIDIA Developer Forums