- It must be a Word or PowerPoint 2010 file saved in a SharePoint 2010 library.
- Everyone editing the file must be using Word or PowerPoint 2010.
- No one has checked-out the file.
SharePoint 2007, SharePoint 2010 and SharePoint 2013 Tips and Tricks which might make SharePoint Life a bit easier!
Click the Connect to Office command on the Library tab of the ribbon, and then click Add to SharePoint Sites.