Поправил колбек

system/API/CallBack.php

@@ -43,6 +43,10 @@ class CallBack extends CallBackAbstract
             'secret_key' => $this->secret_key
         ]);
         $this->confirmation_token = request('groups.getCallbackConfirmationCode', [$this->group_id]);
-        Curl::post($vk, [$this->confirmation_token]);
+        echo $this->confirmation_token;
+    }
+
+    public function sendOk(){
+        echo 'ok';
     }
 }