If you open a word document directly from a synced client folder (synced with OneDrive for Business with the Next Generation Sync client) you may receive the following Upload Pending error

This could happen after a new installation of Office or a defect entry in the Credential Manager. (see below at the end of this blog post)

As you know, for Office documents and collaboration, there is still a cache for all Office documents. Also if you use the Next generation sync client.

Depending of your Office version, you find the access database CentralTable.accdb

Office 2013	C:\Users\<User>\AppData\Local\Microsoft\Office\15.0\OfficeFileCache
Office 2016	C:\Users\<User>\AppData\Local\Microsoft\Office\16.0\OfficeFileCache

First, You should look to an application called Microsoft Office Upload Center and under Settings, look if there is a marker “Delete files from Office Document Cache when they are closed”

If Office is not connected to your services, then the error occurs. You may disable it, but there is a better way:

In Word goto “File” and select account:

You see, there are no connected devices.  You also may see a sign in button

So now you may bring your Office applications directly together to your connected Services. Press Sign in:

The well know Sign in Dialog appears:

And after the end of the Sign In process your local installed Office applications are connected to Office 365 Services

As mentioned before, sometimes The credential Manager has the wrong credentials (or an error) and you have to delete the Office applications stored credentials, before run the steps described above.

So here a picture of the Credential manager:

Alternative you may open a command prompt (CMD) an use “cmdkey /list”

After you have done the steps above, you should not get the error again.

Links:

Delete your Office Document cache
Office Document Cache settings
Use Office 2016 to sync Office files that I open