Resolved HDMI to TV from Windows 10 desktop, sound problem

I have an HDMI cable connected from a desktop to my TV. This brings the video correctly, but have run RCA cables from back of TV's audio output to Aux. input of Home theater for sound. It has been working fine with some adjustments in settings of Windows 10 to stereo mix so still can use computer speakers. Now the sound is not working. Have checked the settings and nothing has changed. Sony TV is showing in sound settings, set to communications, stereo mix. Do you think it has anything to do with Windows 10 updates and how do I fix it?

 

My problem with the set up for HDMI cable to TV from desktop has been resolved. By changing the original HDMI cord which was only one month old, I found that it was defective and had nothing to do with the Windows 10 update or any settings I had altered in the sound settings of the computer. I did not receive any replies from anyone on this as it is a complex set up, but thank you anyway.