[Plugin: WP-FacebookConnect] Invalid Argument

The message explains the problem:

The Facebook Connect cross-domain receiver URL (https://sachistudio.com/blog/<snip&gt;) must have the application’s Connect URL (https://www.sachistudio.com/blog) as a prefix. You can configure the Connect URL in the Application Settings Editor.

You need to set the connect url appropriately in your app settings. FYI, you are using the sociable plugin not the wp-facebookconnect plugin.