If the serial port doesn’t respond while a known good power is applied, that’d be pretty much it. However, you might see if it shows up on your host machine when started in recovery mode via:
lsusb -d 0955:7140
If lsusb shows recovery mode is working, there may be a chance of flashing it, but without a spinning fan even an otherwise working Jetson could be considered for RMA.
One thing to consider which may not be obvious is that anything on USB could be causing a failure as well. Make sure you try the serial port with nothing connected to the USB ports (the odds of this helping are low, but I’ve had USB devices cause boot failure before…in particular I found a USB printer device brought down something like an ATM embedded system which had everyone swapping out other hardware on the assumption directly attached components were responsible).