I tried the Facebook Thumb Fixer plug-in and it wasn't working so I deactivated and deleted it.
From the Facebook, I now get the following error message when I post a link to my WordPress blog:
'Call to undefined function has_post_thumbnail() in /home/gratituderocks/gratituderocks.org/wp-content/plugins/facebook-thumb-fixer/_facebook-thumb-fixer.php on line 139'
I get the same error from the Open Graph Object Debugger under og:description.
I have re-installed, deactivated, and deleted this plug-in repeatedly. I also FTP'd to the directory and no directory existed any more for that plug-in.
How do I fix this problem (at least so the error does not appear any more)?