Hi Jordan,
- Does the sound card supported stereo mix earlier?
- What is the make and model of the sound card installed on your computer?
Firstly, I’d suggest you to visit your computer manufacturer’s website and download and install the latest sound card (audio) drivers.
Note:
If the "Stereo Mix" type device did not show up in the "Sound" window when right-clicking and selecting Show Disabled Devices, it may indicate that you have Integrated Sound, and recording streaming, etc. is not supported. In that case (on a Desktop PC), installing a sound card into an available slot should solve the problem.
Sometimes downloading and installing your sound card manufacturer's latest drivers can add additional sources like What-U-Hear, Stereo Mix, etc.
Stereo Mix is available if the other devices (Microphone, Rear input) are enabled and set as default devices.
In order to enable and make the Stereo Mix available, you would have to right click on Stereo Mix and select ‘Set as Default Device’.
Please post with the issue status.