According to Microsoft, the OneNote sync error 0xE40105F9 occurs when you are using an outdated version of OneNote which is no longer supported by the Microsoft ...

One reason your OneNote Notebook is unable to sync is that your Internet connection is poor. To confirm this, we need to check the bandwidth. You can do this by using one of the free Internet speed ...

Microsoft has released KB5002500 for OneNote 2016 to stop the program from crashing whenever users tried to sync notebooks that were shared to them from newer versions of Microsoft OneNote. Microsoft ...