Fatal error: Cannot redeclare class OAuth2Client (Google+)

I am getting the following error when trying to log in using gmail account. This is not happening to facebook or twitter login (although wordpress login option also gives this error). How do I fix it? Thanks for any suggestions. You can see this live at https://www.maacademyonline.com

Fatal error: Cannot redeclare class OAuth2Client in /home/content/a2pnexwpnas01_data01/64/4042464/html/wp-content/plugins/wordpress-social-login/hybridauth/Hybrid/thirdparty/OAuth/OAuth2Client.php on line 10