Forgive me if you already know this, but after you open audio files (or add audio files to a project) you have to draw them into the timeline.
If that’s not it, are you saying that the audio files are in the timeline, just without the waveform? That would be strange, especially considering you say it happens even with new projects. If that is the case though, are the audio file names still there (in the timeline) or does it say “Media Offline”?