I got a similar error too. But, the first time I installed the plugin, the FIX IT button worked. Then I had to disable it and do some other work to my site files … one of which involved placing the original header.php file back on the server. So, now the FIX IT button will not work.
What fixed the problem for me is to remove the header.php.wpseobak file from the server. Once I did that, the FIX IT button worked.
