Hello, I shorted the inverter from 12V to 5V Arduino boards and nano 328 was 12V =(. Now the flashing red light after inserting the USB but that's all. It did not you tell anyone? I try to upload the bootloader or is it a lost cause? Thanks for the reply.
If you connected the 5V pin (normally a power "source" pin) to a 12V power supply, you likely caused quite a bit of permanent damage. The fact that it no longer responds is a good indicator that you have a failure of the atmega328. Trying to flash the chip will likely have no success. Do you measure 5V at the 5V pin if you plug in USB connector? Same if you use the DC jack?
Desoldering and replacing the AVR chip with a new one MAY work... or you buy a new nano.
If you connected 12V anywhere except "Vin" then it's probably dead.
And upload bootloader failed. ATmega is bad. I will try to replace it. Thanks for the reply.