Xavier NX can‘nt boot and After-sale Service problem

1, I use 11V lithium battery to supply the xn power in a mini-car, But after that, nx couldn’t boot any more.Whether it’s at 19v or 11V.
I’ve tried the following:
(1) Re install the system on the SD card
(2)Replace the bottom board
(3)replace moniter and display cable
but it didnt work and transfer any message from UART.
What the problem and How can I solve it.

2, I am in china ,I contat with the sale company,but the company said I change the power adpter, So the nvidia will refuse to do after-sales maintenance for my nx.
But I think The voltage I provided is according to the instruction voltage in the manual and is not used illegally.so NVIDIA is supposed to repair my nx.

It could be the polarity reverse issue which might damage board. You can follow the RMA process to see how to handle this.

I am not reverse polarity when I use battery,because the nx work normal for a long time under the battey power. but after the haldle, I restart the nx ,it doesn’t work any more.

I follow the RMA process,but cannt contact the online sever. the chat window always display “Searching for an available agent”.

Have you contacted the RAM service successfully?