The Jetson AGX Xavier starts up with a black screen after displaying the Nvidia logo

Hello, I have several sets of Jetson AGX Xavier. The screen of a newly acquired machine turned black when the Nvidia icon disappeared when I started the machine. I have exchanged the card, power supply and motherboard of the machine with another machine that can run, but it still cannot be started up.
I’ve included the video in the link below:
https://onedrive.live.com/?authkey=!AJj5njiYntjjR9w&id=3638216FC8363F0E!131730&cid=3638216FC8363F0E

Have you flashed this unit yet? Do you have a keyboard and mouse connected? If interested in flashing, then I recommend getting the most recent JetPack/SDK Manager listed here and flashing from an Ubuntu 18.04 Linux PC:
https://developer.nvidia.com/embedded/jetpack-archive

Typically a “first boot” after a flash requires the user to create the admin account. I saw a USB error, and perhaps something related to USB (such as mouse/keyboard missing) could interfere.

Also, by far the best method to debug is with a serial console boot log. The docs with a given release provide the information on this, but basically the micro-B USB cable which comes with the AGX is used, and a serial console program running settings 115200 8N1 to the correct serial UART (provided by the Jetson itself; simply connecting the micro-B USB cable to host PC will provide this) is all that is required. Some people use PuTTY as the serial program if on Windows, or on Linux minicom or (my favorite) gtkterm ("sudo apt-get install gtkterm").