The Intel (R) Integrated Sensor Solution driver has been found to conflict with a bunch of processes, and disabling it has fixed the HP Envy keyboard and mouse not working issue for many. Disabling this in the device manager under system devices fixed this for me.

Here is the solution for anyone still struggling with it..... The Intel (R) Integrated Sensor Solution driver has been found to conflict with a bunch of processes, and disabling it has fixed the HP Envy keyboard and mouse not working issue for many. It can be found in the Device manager under System devices.