No sound over HDMI toTV

Hey there,

I am running Windows 8.1 on a Dell. The computer is connected to an 47LG50 TV by HDMI -- in the HDMI 3 port. If I leave the computer running overnight, when I return in the morning, the sound is off and the volume control in my tray is red X'ed out and says “No speakers or headphones are plugged in”. When I click on the volume control in the tray, it runs a diagnostic and comes back to say “Plug in the speaker, headset or headphone”. I have set the computer so it does not hibernate or even have a screensaver. I have tried running a troubleshoot and nothing gets resolved. I've tried switched the inputs on my TV back and forth and no luck there. Please let me know if there are any audio settings I can try on the TV or the computer that would help.

Thanks