Voice Control Not Working

I have a Cisco 9865HDC cable box and a Contour 2 remote with Voice Control. I recently moved our cable box into an equipment cabinet behind the TV.  There is no direct line of sight between the remote and cable box.  The remote stopped working once the cable box was put behind the TV.  I added an IR extender to the box and now we have pretty good functionality with the physical buttons on the remote but Voice Control still does not work.  Besides moving the cable box from equipment cabinet, does anyone know if there's a way to get Voice Control to work?  Thanks.