So I think I found a fix, at least for me, I recently got my self a 5700xt and for the first few days it recorded the audio just fine, then suddenly it quit. Not sure if this will work for everyone.
Open the Sound device menu in the old control panel, not the windows 10 settings menu.
Got to the Recording tab and right click on Stereo Mix and Properties
In the Listen tab, select your default sound device, but make sure you leave the box unchecked that says "Listen to this device" or you'll hear an echo with every thing you do.
Now go to the Levels tab and max out the volume so its not too quiet in the recordings. Apply and does, can close all that out.
AMD Software
Alt+R and click the gear icon on the top right, and go into the General tab
Where it says Audio Capture Device, select the Stereo Mix option
Scroll down a bit more where it says Audio Channels, set that to Stereo
Below that you should see Record Microphone and enable that.
Done!
The only draw back is that your own microphone wont be picked up in the recordings, kinda of a bummer, but I myself can deal without that, if I need desktop recording with my mic I normally use something like OBS.
There can be another work around but its way more complicated, you can also accomplish this with your mic working with Voicemeeter and Virtual audio cable, both are free options from the same site.