debug authtoken call

zimbraSingle.php

@@ -758,7 +758,8 @@ function zimbraSingle_ServiceSingleSignOn($params) {
         return $domainOptions->getMessage();
     }
     $preAuthKey = $domainOptions['zimbraPreAuthKey'];
-    $authToken = new Zm_Auth($params['serverhostname'], $params['username'], $preAuthKey, 'user');
+    $userAuth = new Zm_Auth($params['serverhostname'], $params['username'], $preAuthKey, 'user');
+    $authToken = $userAuth->login();
     logModuleCall(
         'zimbrasingle',
         __FUNCTION__,