If your PC's audio is not working, then there can be an issue with its audio format as well. Check if the sound is muted and if so, unmute.
Windows Users – This option is located in your computer’s control panel, under “Sound”: Mac Users – This Right click the speaker icon in the system tray (lower right corner), go to Sound Settings and then click on “Manage sound devices.” For the output device you want, click “Device properties” and then “Additional device properties.” Go to the Advanced tab and you'll see two tick boxes under a category called “exclusive. It allows for the output signal of the computer to be recorded, capturing live streaming radio for example, system sounds, gaming sounds and so on. Stereo mix is a recording option available on some sound cards that are used with Windows® operating systems.
Stereo Mix will let you open a sound recording program on your computer, choose Stereo Mix as the input and it'll record whatever sound comes out of your computer. You could try to place a microphone next to your speakers, but that's not an ideal way to record that audio. Once you're done updating the audio chipset drivers, check again if the missing device will appear. We suggest checking the device manufacturer if there are available updates for the drivers.
Your audio chipset drivers may be outdated, that's why Stereo Mix does not appear in the list of devices. You should see a “Stereo Mix” option appear. In the pane, right-click on a blank area, and make sure both “View Disabled Devices” and “View Disconnected Devices” options are checked. Go down to the audio icon in your system tray, right-click it, and go to “Recording Devices” to open up the proper settings pane.