Hi @sns ,
The same OneNote file is synchronized in the sharepoint online of the old PC, but it is not synchronized in the sharepoint online of the new PC?
Please copy data to new page/section:
For any other section/page that's corrupt, we suggest you copy and paste the pages in the section or content in the page into another section/page. Right click on the problematic section and select Move or Copy. Then select Copy and select the same notebook. Then delete the original (corrupted) section/page.
More possible solutions, please refer to:https://support.microsoft.com/en-us/office/fix-issues-when-you-can-t-sync-onenote-299495ef-66d1-448f-90c1-b785a6968d45
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