To reconnect a workbook: 


  1. Open OneNote
  2. In a web browser, navigate to portal.office.com and login with your email address
  3. Select OneNote
  4. Select My Notebooks
  5. Open the desired notebook and select "Open in OneNote"
  6. If a pop-up appears, select "Open in OneNote 2016"
  7. OneNote will open, and a security pop-up will appear. Select Yes to continue 
  8. The notebook will now begin to sync into your OneNote.


Advisory:

Once notebooks are open in client - close the duplicate ones that are no longer syncing and then check the sync status on all of them and compare to what you have in office.com - notebook.