hdmi not plugged in. simple solution
Website last updated: Saturday April 27, 2019
After upgrading to Windows 10, the sound output from my computer's HDMI socket ceased working. All the connections were obviously OK as the video output, (to my lounge TV), worked fine. I looked all over the internet for a fix and found plenty but none that worked for me. I found this simple cure by experiment. This only applies if you have an NVIDIA video card I believe.
First check out your sound configuration by typing "sound" (without the quotes) into the Windows search box at the bottom left of the taskbar, (or going through the control panel) and you will bring up this box. Note the top options which are grayed out and it says "Not plugged in". (If it's not grayed out this cure won't work)
Now right click on the desktop and click on NVIDIA control panel. This will open up the main control panel for the NVIDIA video card:
Go to the "Display" menu on the left hand side and click on "Set up digital audio. The window shown above will open. Go to the HDMI drop down box in the main panel and click on the down arrow next to HDMI. Make sure your monitor is selected and click on "Apply".
Now go to "Open Windows sound settings" to get back to the original "Sound" menu. You will see that the HDMI option is no longer grayed out. Click on it once then click "Set default" at the bottom. You should now be able to get both video and sound from your HDMI output on your computer.
Footnote: Since writing the above, I've had this problem again with a twist. Despite doing all the above it still wouldn't work and I eventually discovered that you need to disable "Speakers" as shown above BEFORE you try to enable the HDMI output. Also the problem may be cause by out of date video drivers. Just to make sure, download driver booster from here and run it. It's free.