When I plug in the Xavier NX with a 12V 5A power supply and HDMI cable I get a green light and the fan turns on but the monitor does not produce any output.
How do I debug this issue? It is a production board so I don’t have an on-board micro sd card to reflash.
Are there any docs for how to get started booting from the eMMC?
You’ll want to save a serial console boot log and post that here. There is a chance that the system is fully functional other than graphics setup. See (Nano and NX have the same serial console setup):
https://www.jetsonhacks.com/2019/04/19/jetson-nano-serial-console/
One common issue is that sometimes people cross the SD card image and the eMMC image…the two are not interchangeable. Also, a production eMMC module does not arrive with any software, and so it would have to be flashed. Mostly flash would use JetPack/SDKM from an Ubuntu 18.04 host PC. The most recent release is recommended, see:
https://developer.nvidia.com/embedded/jetpack-archive
(includes some docs on flashing)
Also, beware that alternate carrier boards typically require different firmware (device tree) from the carrier board manufacturer.