If you are using browser Twine with Safari, one possible explanation is that, unfortunately, your browser may have erased your work if you haven't used Twine in a week.
You may have also accidentally deleted your stories by clearing your browser history or removing a profile from your browser.
To see what is left, open your browser local storage. Any
stories will be listed with keys that start with
passages will be listed with keys that start with
twine-passages. You may be
able to recreate your work using this information.
Unfortunately, if you don't see anything in local storage, you will need to restore your work from a backup.
If app Twine doesn't show any stories, check the contents of your story library folder. If you see files there that Twine isn't showing, then there's something wrong with the files that is making Twine think that they are not story files. Try opening them in a plain text editor; if the problem is obvious, you might be able to edit them directly, or you might be able to recreate the story using this file. The underlying structure of these files is documented here.
This is most likely caused by Twine having trouble with some aspect of your story, for example if the HTML structure of your story file became damaged. If you see the file in your story library folder, try opening it in a plain text editor. As above, you might be able to edit the files directly and repair them, or recreate your story using them as a guide.