This isn’t a Windows thing, it’s a firmware thing. It’s HP’s doing, and HP is well known for screwing with the usability of their devices. In my case, on my Victus, it’s F10 that opens UEFI, but the menus are incredibly stripped down. Looking online, F10 seems to be the key to access it on your device, too. Maybe you just aren’t getting the timing right, sometimes you gotta mash the absolute hell out of that button to get it to register. Once you do get it, setting a post delay will make it easier in the future.