RMA Jetson Nano wont boot up. However green LED works.

Hi Wayne! I connected a Nvidia Jetson Nano 2GB device with USB TTL and used windows PUTTY in doing so. USB TTL was COM5, baudrate 115200, but no information was visible when I started the device. USB TTL voltage level 3.3V RX TX CP2102. There was no good result. I did as @mehmetdeniz was told here, but I only have windows running.
I was disappointed. I need technical support, and I send it through the post. I don’t know where to send it.