The Office Upload Center is what handles syncing to SharePoint. When a file is checked in or closed, the upload centre will then sync and replace the file on the server with your local cached copy that you’ve been working on. Sometimes, if the document gets stuck in a pending or failed state, it can cause issues with checking in and out the documents. To fix this, you can clear the cache.

The first thing to do is open the Office Upload Center. This can be done simply by searching it from your start menu. Once opened, open the settings.

In the settings, there will be an option to ‘Delete Cached Files’.

You’ll then be prompted to confirm, just select ‘Delete Cached Information’. Hope this fixes any SharePoint sync issues for anyone!