There could be a few possible causes for this. One possible culprit could be a dead battery - either just bad or simply not being charged. To test this, remove the battery (HP Maint. Guide here - https://h10032.www1.hp.com/ctg/Manual/c06435950.pdf), put the laptop back together (minus battery), then see if it will run on AC power. If so, then a simple battery replacement will resolve this. If it still won't power on, then I would look at the charging cable itself (perhaps try a different one if available, or if you possess the necessary tools you could test it to determine it is functioning correctly), then the motherboard starting with the AC port. I also am wondering if you have reached out to HP support and if so, what they advised. One other possibility comes to mind (assuming the laptop still doesn't power on with battery removed), though since you asserted the OS/etc is up to date I admit this is fairly unlikely - I have seen various laptops (differing manufacturers - Alienware/Dell, HP, etc) actually stop charging the battery if the OS is not up to date - while no one in the various support departments have been able/willing to explain why, the fact remains that laptops seemingly unable to charge suddenly started charging again when the current patches/etc were installed.