File won’t open

I went to open a particular file and got a warning saying it was either open on another computer or hadn’t closed properly. It said to continue if it wasn’t open on another computer, which it wasn’t, so I clicked that.

And now the program doesn’t open at all and when I search for the file in programs and try to open it there, I get the below message. Also all my other files open fine.

EDIT: I also tried opening an earlier version of the file I had saved as a backup via email, and that wouldn’t open either. And it didn’t help when I actually tried opening it on a different computer.

OKAY, apparently I was dumb and forgot to UNZIP my backup files. So I recovered a slightly older version of the file and saved it to a new location.

But I’m still curious if anyone knows what happened? I managed to open the old file after a bunch of tinkering and all the chapters were there and named, but the text was missing.