A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
Hello,
Welcome to Microsoft Community and thank you for posting your query.
Let us try creating new Notebook, copy the some section of the not syncing notebook to new notebook, move it to OneDrive and check if they sync. If the notebook doesn’t sync as expected, try copying the data from the section to new section and then try to sync.
For more information on best practice to sync notebook, please refer the below mentioned article.
https://support.microsoft.com/en-us/kb/2819334
Please post back with the updated issue details for further assistance.
Thank you.