OneNote for Business and SharePoint - cannot export notebooks

Notebooks created using OneNote for Business or SharePoint cannot be exported and transferred to a OneNote Personal account.

Details

"Exporting and importing notebooks through OneNote Online is only available for notebooks stored on personal OneDrive accounts, not for notebooks stored on OneDrive for Business or SharePoint. For information about exporting notebooks to PDF files from OneNote 2016 for Windows, see Export notes from OneNote as a PDF."

Quoted excerpt above from article Export and import OneNote notebooks.