Audio from recordings no longer plays

[rumorconsumer]

Using a Mac mini M1. I have a ton of recordings both the video and audio files and somewhere a few months ago the Mac stopped playing the audio. QuickTime Player opens, the audio file progress bar moves, but no audio plays. It's as if the track is blank. If I open the audio in VLC or another player app, it works fine. So it seems that Quicktime has forgotten the codec? I don't get it. Any thoughts?