I would make sure you have the latest BIOS update installed... There is a setting in the BIOS (Battery Health Manager) that if set to Maximize My Battery Helath, will stop charging at 80% to help limit the exposure to battery failures due to constant, excessive charging, something that seems to be common these days
also, if you use the HP Support Assistant, it has a Battery Check tool that can tell you the status of the battery... The tool obtains information directly from the battery that Windows can't do
I work for HP. However, all opinions and comments are my own.