Sounds like something’s stuck. You could try the “Without Files” option in the Ctrl key open dialog, then when that’s open save again as Default Layout, and re-open Ctrl key Default Layout.
There’s probably a pref file that could be deleted in the audio file workspace prefs, but I’d try that first.
Or you can go to the workspace layouts menu and define default or custom named layouts while in the audio file workspace, and in the montage workspace.