Hi. In present days 2025,sound problems appeared in Windows 11 latest version and vmix older than 27 version. If this is not your case,give more details for your setup or contact vmix support

Have you seen in Vmix-->settings--->Audio outputs,what is there? Is same like before? If you play any video or audio input,there is no vmix audio output? Vmix audio mixer,when you play anything that has sound shows the audio bars from the running input?
The audio bars in the main vmix gui are visible?

The master output is "Default Windows Playback Device."

I changed it to something else, let vMix restart, changed it back again to "Default Windows Playback Device," let it restart again, and tested it. It still isn't outputting my mic signal.

When I add an audio file and do a quick play of it, I DO SEE the audio bars on both the input and the master audio output, and I hear it in the speakers as expected. This is not the case for my mic where I only see the lines on the input and nothing on output.

Even though vMix is showing the audio bars for my mic input, even though my mic comes in fine in other programs, and even though it plays an audio file perfectly, I don't see or hear any sign of an output from vMix for my mic.