Audio Tracks Flat after Audacity Crashed


I’m working on OS X 10.13.6 and Audacity 2.3.2
I’m a bit new to Audacity, so any help would be appreciated.

I was working on a project with several tracks and I clicked “Sync-Lock Tracks”. I then made an edit, pressed cntrl-Z to undo the edit and Audacity crashed. I re-opened Audacity and restored the project, but when it was restored all tracks were flat lines. Audacity said there were damaged files so closed immediately, so re-opened. Audacity still said there were damaged files I clicked delete damaged files, but the tracks are still all flat. I can still see a shadow where I used the envelope tool, but there is no audio on any of the tracks.

Not sure what I did wrong. I have a .wav file backup, but it would be much much easier to finish the project with all the tracks intact. Any way to reverse this or at least prevent it in the future?