You might want to try resetting your NVRAM/PRAM to solve this issue, otherwise create a backup with Time Machine and then reinstall macOS and try again. If you don’t see any output devices at all, you might have encountered a problem when updating or upgrading macOS. Some sound issues can even be fixed by selecting a different output, then selecting the original output. If you would rather output to another device like an audio interface, headphones, or aggregate device, you can specify that under these settings. Now, test your output settings again by playing some music or an audio file.

If something other than Internal Speakers is selected (and you have no reason for that to be the case), then click on Internal Speakers to reroute the audio. You should see a list of devices that you can use as sound outputs, with the default option (on most Mac computers) being Internal Speakers. Check the volume slider at the bottom, and uncheck the “Mute” box if necessary. Click on the “Output” tab and take a look at where your audio is being routed. The first place to check if you are having audio problems is macOS Sound preferences. No Audio on Your Mac? Check Sound Preferences

5.1 audio interface for mac 2017