A603 carrier board with Jetson Orin NX 16Gb - failure to boot after flashing is sucessful

Hi.

I have a A603 carrier board that I want to use with a jetson Orin NX 16Gb module. i followed the the guide from the wiki to install Jetspack 6.0
A603 Carrier Board | Seeed Studio Wiki
I want the flash to be internal only - without an SSD or a USB flash drive.
I followed the instructions but I removed the --external-device command line option. The flashing operation seems to be sucessful - it goes to the reboot device step - the jetson boots - the fan works. It then seeks to do a network boot connection. It fails and I arrive on a black screen - UEFI Interactive Shell v2.2. The USB keyboard seems to not be detected.

What should I do?

Thanks