Recently updated to Windows 10; Stereo Mix not recording audio

When my computer was using Windows 7, I used Stereo Mix a ton for recording sound. However when I updated to Windows 10, it doesn't work anymore. I updated drivers, and from there enabled Stereo Mix again. The issue I'm encountering is that for some reason after the update, Stereo Mix doesn't want to record any sound regardless of anything I've tried. I've tried switching sound devices, making it my default microphone, my drivers are fully updated, I've attempted disabling 'Listen to this Device', etc. Nothing works in multiple programs.

In my case it was: "Computer sound must go through the sound card. Using HDMI to output video and audio will bypass the sound card. Sometimes the only way to force it, is to connect any kind of speaker." (from harrymc answer) To clarify there was a usb headphones which I used as playback device. And Stereo Mix was recording silence. Turns out Stereo Mix only records sound which goes through same audio card Stereo Mix itself belongs to. That was a hard part to understand for me. You need to set that card as playback device to be able to record sound. Posting this as it took several hours for me to understand that.