If you choose Link attachment type: Share a link to your blogpost then from Facebook’s point of view you are sharing the link. It means that your content MUST have one link. Just one and only one.If you got this error then your content has more then one link and Facebook got confused which link you want to share. Please make sure that you don’t have any links in the post text or you don’t use %SURL% in the message format. If you need more then one URL in your post then switch Link attachment type to Attach your blogpost