Greetings,
Welcome to the forum.
I am not a HP employee.
A HP 500 PC can be many products. I can't zero in on your specific PC.
It looks like the 500 series PC is circa 2015.
Running HP UEFI boot time diagnostics may locate bad hardware but your PC will not POST.
This symptom generally suggests the motherboard may have failed. Or the power supply has failed.
It could be any component connected to the motherboard.
I suggest having a local PC tech take a look. Can't troubleshoot this PC's problem in a forum.
Regards