When using the WP feature that allows you to move wp-content to another location and define it like so (in config.php):
define( 'WP_CONTENT_DIR' , $_SERVER['DOCUMENT_ROOT'] . '/fac/wp-content' );
define( 'WP_CONTENT_URL' , ' http://myurl.com/fac/wp-content' );
It is very likely that this line (saml-20-single-sign-on/saml/www/_include.php, line 25)
Will not be pointing to the right folder. This is a hard coded absolute value, so for now in order to get this plugin to work you need to change this value to point to wp-blog-header.php in your wordpress directory.
I assume the plugin developer will fix this in later versions.