A warm welcome to HP Forums!This is a great place to get support, find answers and tips to your technical queries.
If you have tried all possible steps available in this document, then I'm afraid, its a possible hardware failure and you may call HP Support to obtain all available repair/replacement options. I've send you a private message with instructions on hot to contact your regional HP Support. Could you please check your inbox on the forums page for the private message.
Have a great day!