There is no official AMD responses in this forum - unfortuantely. AMD depends on their customers to supply tech support to other AMD customers. It's NOT a good situation at all as far as Customer Support at AMD, IME of many years.
That being said OE CPUs only generally have a 1 year warranty. Boxed CPUs have a 3 year warranty. HP can decide their own waranty. It's hard to say if the CPU has actually failed without installing it in another system that is working to see the results. You could have something as simple as the power on switch failed or a power cable connection bad, etc.
I would certainly try to e-mail AMD tech support and see what they offer, but I would not get my hopes up as they have provided very poor and little service in the past 10+ years, IME.
Building a reliable PC involves more than just assembling the parts. You need to be able to configure all of the BIOS settings appropriately. This can be quite involved and frustrating as it can require a lot of trial and error with stress testing. It is however often the only means to get a 100% reliable PC.