Please go to your Meetup OAuth Consumers page https://secure.meetup.com/meetup_api/oauth_consumers/ , create a consumer, and in the line 22 set the client_id to Key and client_secret with Secret. The Callback URL must be http://erp.leaf.com.my/webmail/modules/OAuthIntegratorWebclient/Classes/OAuthClient/login_with_meetup.php Make sure the Website URL is not in a private network and is accessible to the Meetup site.