Hi, I am having the same problem, I do have HDMI (ARC) on both the TV (LG Smart 4K) and on my LG external speaker. I do have the HDMI hooked up to both the ARC connections on the TV as well as the speakers and yet I have no sound on anything when the TV is on TV & external speakers, no sound on just external speakers either - only sound when I have TV speakers only. I also bought the Digital Optical Audio cable as both support that and still no sound, please advise thanks