Hi,
First, make sure you are following the correct steps to flash the Jetson Xavier AGX. Here’s a webpage with all the necessary information: NVIDIA Jetson Xavier AGX.
Additionally, you could try using a different cable or follow the suggestion from this post where they had a similar issue: The connected Jetson device is not ready for flash.
As mentioned there, you could also try disconnecting other unnecessary USB devices, connecting to a different USB port on your host computer, or even testing on a different computer.
Jose Morera
Embedded Software Engineer at RidgeRun
Contact us: support@ridgerun.com
Developers wiki: https://developer.ridgerun.com
Website: www.ridgerun.com