This is the third sony HDMI TV I am using for my computer monitor, and this is the third one that has lost its sound capabilities. Is there any thing I should know about your cards. I am using the AMD Radeon R7 200 on this TV.
When you installed any drivers did the installed install HDMI audio drivers? Is a device listed in Device Manager? Is it enabled or missing in Playback Devices window?
All driver are installed, the device is listed in Device Manager, and it is enabled as default device in playback devices window.
And when you ask the Sound window to test the HDMI audio device, is the green noise bar moving at all on the right of the device?
This would indicate the sound is being rendered and is leaving the GPU, providing the HDMI output is your default audio output. Do you have means to check the cable at all?
If the HDMI sound device is testing correctly but the sound isn't playing off of the TV you want it to, it would seem the issue is with the cable or TV itself. It only ever passes 2 channels so shouldn't be anything setup wrong. Is your only choice to use the HDMI interface for audio or can you resort to an AUX cable?