Jetson nano not booting up...URGENT

You two may have different cases but the debug method is the same.

Please dump the uart serial console log. Before dumping this log, remove the “quiet” keyword inside /boot/extlinux/extlinux.conf on your sdcard image rootfs.

https://elinux.org/Jetson/General_debug

For @nisar.bukhari, I would suggest you could also try other monitor too.

And for @kozinov.andrey, please make sure you are using 2GB sdcard image but not Nano-4GB sdcard image.