WP-FB-comments – Fatal error: Uncaught OAuthException: Malformed access token

I am trying to use WP FB Comments Plugin.
I did following
1.Installed this plugin.
2. Created a facebook app , setting App Domains url and Site URL
3. Created a facebook fan page
4. Filled the settings form /wp-admin/admin.php?page=wp-fb-comments with Application id , API key, Application secret, Facebook Page id
5. Clicked Save change
6. Clicked Connect Admin FBacc
7. Gave permission to this application ( click Allow )
Then the process was redirected and I got this following error.

Fatal error: Uncaught OAuthException: Malformed access token ABADoExZCOJ0RABAC1OWB4ZAdSKLNA32RAcZCLrtTKtXrVCthe3kLoiZCMkCcGevx1bZCbkOLtiEIi6VxeZCvviJ5yFf9GAHBxRqtPqoJvBWQJSgZD&expires=5183998 thrown in ..public_html/TEST/wp-content/plugins/wp-fb-comments/facebook.php on line 543

I tested this plugin in my two different server. Same error I found.

If anyone know what is my mistake please help me.

https://www.ads-software.com/extend/plugins/wp-fb-comments/