Wordpress Facebook login button not loading

Hi I am getting this error message on Wordpress facebook login button, they are running on Ubuntu.

I have already checked with theme provider and checked all the configuration are correct.

Please could you advise what might be the issue.

Failed to load resource:
        the server responded with a status of 500 (Internal Server
        Error) 

      
POST http://www.xxxxxxxxx.com.mm/wp-admin/admin-ajax.php
        500 (Internal Server Error) 

      

      Details of the error:

Remote Address:  128.199.180.xxx:80
Request URL:  http://www.xxxxx.com.mm/wp-admin/admin-ajax.php
Request Method:  POST
Status Code:  500 Internal Server
            Error
Request Headersview source
Accept:  */*
Accept-Encoding:  gzip,deflate,sdch
Accept-Language:  en-US,en;q=0.8,nl;q=0.6,ro;q=0.4,es;q=0.2,it;q=0.2,ru;q=0.2
Connection:  keep-alive
Content-Length:  55
Content-Type:  application/x-www-form-urlencoded;
              charset=UTF-8
Cookie:  wordpress_4c37716057a1ac67a1724c4b5a846374=contact%40xxxxxx.com.mm%7C1405587466%7C895bfc4def5a2f6ee78ee46a80ff2824;
              PHPSESSID=ego6frr98tv0mb0a74t9tts3r7;
              wordpress_logged_in_4c37716057a1ac67a1724c4b5a846374=contact%40xxxxxx.com.mm%7C1405587466%7C14c2bf4689423c387dbbb6e4597d7e85;
              wp-settings-1=mfold%3Do%26property_types_tab%3Dpop%26editor%3Dtinymce%26libraryContent%3Dupload%26imgsize%3Dmedium%26align%3Dcenter%26hidetb%3D1%26wplink%3D1;
              wp-settings-time-1=1405414672


User-Agent:  Mozilla/5.0
              (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like
              Gecko) Chrome/35.0.1916.153 Safari/537.36
X-Requested-With:  XMLHttpRequest
Form Dataview sourceview URL encoded
action:  wpestate_ajax_facebook_login
login_type:  facebook
Response Headersview source
Access-Control-Allow-Credentials:  true
Access-Control-Allow-Origin:  http://www.urldeleted.com
Cache-Control:  no-cache,
              must-revalidate, max-age=0
Connection:  close
Content-Length:  0
Content-Type:  text/html;
              charset=UTF-8
Date:  Tue, 15 Jul 2014
              09:00:17 GMT
Expires:  Wed, 11 Jan 1984
              05:00:00 GMT
Pragma:  no-cache
Server:  Apache
X-Content-Type-Options:  nosniff
X-Frame-Options:  SAMEORIGIN
X-Powered-By:  PHP/5.5.9-1ubuntu4
X-Robots-Tag:  noindex