Logic Pro X: No sound when using audio file editor

[v10.5.1 on MacOS Mojave on a 2016 iMac]

Hi folks! I hope somebody can help me with this.

I've had this problem a few times over the years (on different versions of both Logic and MacOS and different computers) and, when it's been resolved, I've never quite figured out what I did to fix it. So...

My understanding is that, when I open a region in the audio file editor, I should just be able to play the file (or selection) in the editor and hear it. But, for some reason, it's not producing sound. If I can hear the track when playing the project, I should hear the file in the editor, right? The audio output is correct. The file format is compatible. The track is either in solo mode or otherwise not muted. And the volume is at a reasonable level (not at -∞). So what's the issue? I expect it's something very simple (it usually is, isn't it?).

Thoughts?