Federicoviola

Thanks Beau for your answer.
But I don’t think that the problem were that. I’ve tested this service with only this piece of code:

class Keyring_Service_Mendeley extends Keyring_Service_OAuth1 {
	const NAME  = 'mendeley';
	const LABEL = 'Mendeley';

	var $authorization_header;
	var $authorization_realm;

	function __construct() {
		parent::__construct();

		// Enable "basic" UI for entering key/secret
		add_action( 'keyring_mendeley_manage_ui', array( $this, 'basic_ui' ) );

		//$this->authorization_header = true;
		$this->authorization_realm = "https://www.mendeley.com/oapi/";

		$this->set_endpoint( 'request_token', 'https://www.mendeley.com/oauth/request_token/', 'GET' );
		$this->set_endpoint( 'authorize',     'https://www.mendeley.com/oauth/authorize/', 'GET');
		$this->set_endpoint( 'access_token',  'https://www.mendeley.com/oauth/access_token/',  'GET');

		if ( defined( 'KEYRING__MENDELEY_KEY' ) && defined( 'KEYRING__MENDELEY_SECRET' ) ) {
			$this->key = KEYRING__MENDELEY_KEY;
			$this->secret = KEYRING__MENDELEY_SECRET;
		} else if ( $creds = $this->get_credentials() ) {
			$this->key = $creds['key'];
			$this->secret = $creds['secret'];
		}

		$this->consumer = new OAuthConsumer( $this->key, $this->secret, $this->callback_url );
		$this->signature_method = new OAuthSignatureMethod_HMAC_SHA1;

		$this->requires_token( true );
	}

And it works but returns me in WP a blank page. In the browser I get the following line:

https://192.168.1.40/wordpress/wp-admin/tools.php?page=keyring&service=mendeley&action=verify&kr_nonce=597fcb6eff&nonce=e78d6c2116&oauth_token=a9b3e0b01c0ce48abcb5e19788e03b65050bf2092&oauth_verifier=949c5605a1

The twitter service works and return in the browser the following line:

https://192.168.1.40/wordpress/wp-admin/tools.php?page=keyring&service=twitter&action=created&id=59&kr_nonce=ed950fe3d3

The &action is different. I don’t realize why…
BTW I based my code in the twitter template.