I have a hp probook 4540s, with product number C4Z14EA#ABB.
When I press the power button, the power light flashes 9 times, the ninth time with a slower duration.
I don’t see any other signs of life in my pc: no fan spinning, when I connect a phone to my pc via USB port, it doesn’t charge.
When I try power reset, my computer doesn’t start. It flashes like I start it without power reset.
I think that might be a hardware issue. I really hope it is not but I am not positive - when I tried to uninstall the battery drivers in windows and restarted the pc, I didn’t see any change. If I start the probook except the windows I may run Ubuntu 18.04 but I don’t know if it will help.