A family of Microsoft products that enable users to capture, organize, and reuse notes electronically.
Your current problem might be different than the recently solved syncing issue. Its probably an issue with the client itself. I don't know if clearing the cache would actually solve your problem but its worth a shot.
If you are going to clear your cache, I suggest that instead of actually deleting the folder (C:\Users[Username]\AppData\Local\Microsoft\OneNote\15.0) you just rename the folder to something different. This way, onenote will treat it as being deleted while allowing you to still save the old cache in case something goes wrong.
You can also save backup copies before you actually clear your cache. There are a couple ways of doing this:
-copying a backup copy from your backup folder
-pressing backup now from the backup options
-exporting the notebook to a package that can then be reopened later