That’s possibly a different issue. I think I saw multiple Topics on this, but here’s one:
https://forum.shotcut.org/t/bug-report-drag-and-dropping-video-into-the-timeline-randomly-stops-working/3547
Which also links to this Issue in the source code repository:
https://github.com/mltframework/shotcut/issues/326
If restarting Shotcut (save to a backup file first) doesn’t fix it, try using the suggested other methods of adding clips to a timeline; “Paste, Append, Insert, and Overwrite.”. Append is the big plus sign in the timeline editor, paste is the clipboard. Select your audio track, select the clip in e.g. the playlist, then try one of those buttons.