Facebook & Google+ Like Button didn't appear on Pay with a Like Plugins

i installed "Pay with a Like" plugins to my blog. when tested with one of the posts, the facebook & twitter button didn't appear at all,

=> http://goo.gl/z5ds8h

when tried to play around with the social button setting and saved, appear this error,
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Fatal error: Cannot redeclare class Facebook in /home/vitamin/public_html/ireach.my/wp-content/plugins/pay-with-a-like/lib/facebook-php-sdk/facebook.php on line 160
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Pls advice whats the problems and how to rectify. tQ