My spouse had the same problem with her HP a few months ago.
Does the battery still accept a full charge when you plug it in? If not, you may have a problem with the inboard power supply where you plug in the power source not allowing the full charge to the battery.
If this is not the problem, you should be able to go into the control panel and go into "All Control Panel Items". Then click on the notifications and reset the battery notification.
Hope this helps.