Starting April 11, 2017 many customers started having trouble with OneNote not syncing with Windows Phone.
Since Apr 11, 2017, many users are having problems with OneNote not syncing with Windows Phone thru OneDrive. When you try to open a notebook on the phone (8.1) in OneDrive, you will receive the error, "We can't complete this task. Try again. Error code: 80004005". I did get one notebook to open thru the Office app that was stored in SharePoint, but non stored on OneDrive. (I also noticed but perhaps that has been for a while or maybe it's related that when using the Office app to open files on OneDrive it won't, instead you have to tap on "..." and select to "open in OneDrive". Thus, no longer able to open OneDrive files thru the Office app, now apparently can be opened thru the OneDrive app. While that is not a problem to open them that way, I am mentioning this in case it also has to do with OneNote not syncing thru OneDrive and OneDrive notes therefore not available on the phone - perhaps the OneNote files previously synced thru the Office app, not OneDrive and now OneDrive is the only app able to access OneDrive data.) Will you please fix this so OneNote files stored on OneDrive are available on Windows Phones (8.1). By the way, I cannot update my HTC M8 phone to Windows 10 (you don't provide that), so that is not a solution.