title: Why can't I publish my Excel Add-In?
body: <p>I have updated an Excel add-in that used to work fine apart from some new requirements. I've added the new functionality, tested it and all is well so now I need to publish it. When I hit the publish button in Visual Studio 2010, I get the error, "Cannot publish because a project failed to build". However, the project is building perfectly.</p>
  
  <p>How can I get the the bottom of this problem and publish my updated add-in?</p>