I have an A/V question. I just mounted 5 LG TV's in a few offices. I terminated each end to a HDMI keystone, and the length of the HDMI run is approx. 15 - 20 ft. I'm connecting the PCs to the TVs as a third monitor. Of the 5, two are working without an issue, but i'm having issues with the other three. The OS and the graphics card is detecting the TV as a third display, but after choosing the correct input on the TV, it's still displaying "no signal". This is the case for all of the displays that aren't working.