Explain what you have on HDMI 1. It's very unusual to have "Live TV" on HDMI.
Where I'm going here is that most TVs can't pass HD AUDIO. Some can't process some HD audio encodings so if this LIVE TV is on HDMI then at the source I would change the AUDIO ENCODING to Stereo or PCM and retest.
I have a 3 month old 43in. Smart LG tv. Just 2 days ago I lost audio on the live tv. Using netflix or a dvd through the tv I do get sound. However, as soon as I go back to Live tv on HDMI 1, I have zero. I have tried a factory reset, and also unplugged the power cord and held down the power button on the tv for 30 seconds ( was told that by a LG rep.) I have also done the sound test on the tv, and was able to hear the music fine. Any ideas on how to possibly get sound back while watching TV?? Much thanks!