If the Volume Knob on the keyboard isnt working properly, please use Window's Search tool to look for and open "Services.msc." Scroll through and open "Human Interface Device Access." Make sure the Startup Type is set to "Automatic" and below press the Start and Stop buttons to Stop and restart the service. After you have done this, hit APPLY and OK.
Models: KB501, KB577U, KB588U, MGK1-xx, MGK-L80-xx