生成运单接口

请求参数：{"app_token": "app-0b25ec04-0705-468e-8534-357b9463ef88", "add_source": "2", "wx_appid": "wxc5d78102e3099928", "openid": "123", "delivery_id": "SF", "biz_id": "SF_CASH", "custom_remark": "易碎物品", "tagid": 111, "expect_time": 1604897873, "sender": {"name": "吴芸芸", "mobile": "13818880655", "province": "上海", "city": "上海", "area": "徐汇区", "address": "宜山路700号普天产业园C5栋"}, "receiver": {"name": "王业帆", "mobile": "18501737516", "province": "上海", "city": "上海", "area": "徐汇区", "address": "漕河泾开发区田林路388号兴业大楼"}, "cargo": {"count": 1, "weight": 1, "space_x": 1, "space_y": 1, "space_z": 1, "detail_list": [{"name": "马蹄莲", "count": 1}]}, "shop": {"wxa_path": "http://www.mp.com/order", "img_url": "http://pic", "goods_name": "进口马蹄莲", "goods_count": 1}, "insured": {"use_insured": 0, "insured_value": 0}, "service": {"service_type": 0, "service_name": "标准快递"}}

返回：生成运单成功

{"errcode":0,"errmsg":"ok","order_id":"be9bf882223f11ebaa82f48e38dd0dc8","waybill_id":"SF6026131434978","waybill_data":[{"key":"abFlag","value":""},{"key":"cargoName","value":"\xe9\xa9\xac\xe8\xb9\x84\xe8\x8e\xb2"},{"key":"codeMapping","value":""},{"key":"codingMappingOut","value":"3A"},{"key":"destEncodePhone","value":"185****7516"},{"key":"destRouteLabel","value":"B16-G-021BA-040"},{"key":"destTeamCode","value":"040"},{"key":"destcode","value":"021"},{"key":"filter_result","value":"2"},{"key":"limitTypeCode","value":"T4"},{"key":"origincode","value":"021"},{"key":"printFlag","value":"000000000"},{"key":"printIcon","value":"0-0-0-0-0-0-0-0"},{"key":"sourceTransferCode","value":"021WF"},{"key":"twoDimensionCode","value":"MMM={\'k1\':\'021WG\',\'k2\':\'021BA\',\'k3\':\'040\',\'k4\':\'T4\',\'k5\':\'SF6026131434978\',\'k6\':\'\',\'k7\':\'7ebab4bc\'}"},{"key":"xbFlag","value":"0"}],"is_correct_sender":0,"is_correct_receiver":0}

问题：查询运单轨迹为空，请问是什么原因？