You didn't specify the operating system your notebook is using and in this case I will provide you with the link to the list of official supported systems. From there chose the corresponding one your notebook has and navigate to the bottom of the page and look at
Software sections and download
HP Quick Launch Software plus
HP On-Screen Display Utility.
After you download these utilities, run them and follow the instructions provided by the wizard. Reboot your notebook and your hotkeys will work again.