If you have experienced the following problem in the Notebooks app:
After signing in, notes are properly downloaded in the Notebooks app, but when you exit and return to Notebooks, the notes have disappeared.
This is due to one of the notes being a very large note. The maximum size of a note is 64K. When the size of a note is more than that, the note data cannot be saved to the local memory, resulting in notes “disappearing” when returning to the app.
To solve this issue, goto the Notebooks app in your web account, delete the large note and instead copy its contents into a Text or Word file, then Attach the file to a new note.