To recover a section or notebook from a corrupted OneNote file, you’ll need to follow these steps:

1. Keep the notebook open. After the error message appears, do not close OneNote. This will prevent the potential loss of any changes that have not been saved divergently.
2. Check for an available backup version. OneNote may have automatically created a backup in the same location as the notebook file.
3. Rebuild the notebook index if a backup version is unavailable. To do this, open the notebook using a text editing program like Notepad.
4. Delete and recover a damaged section file. If rebuilding the notebook index doesn’t yield any results, you’ll need to delete the corrupted section to recover the notebook.