This helped to solve my issue and successfully flash to NVMe from the command line:
Download the following two files (I pasted the links into my browser while I was logged in with my nvidia dev account).
https://developer.nvidia.com/assets/embedded/secure/tools/files/jetpack-sdks/jetpack-6.1/Jetson_61_b218/Jetson_Linux_R36.4.2_aarch64.tbz2
https://developer.nvidia.com/assets/embedded/secure/tools/files/jetpack-sdks/jetpack-6.1/Jetson_61_b218/Tegra_Linux_Sample-Root-Filesystem_R36.4.2_aarch64.tbz2
Then continue as described in Quick Start — NVIDIA Jetson Linux Developer Guide 1 documentation