调用https://api.weixin.qq.com/cgi-bin/message/mass/sendall微信群发接口，群发图文消息

参数：{"touser":["ouikY6pGs7P0NbWBVjGQfzS0NuGY"],"mpnews":{"media_id":"y1ak-JEhu68DyasNcGZ93m1a49oRKudZbzQfqVKTy6FsVLh8i_5BDJjb9XiVX2J0"},"msgtype":"mpnews","send_ignore_reprint":0}

返回错误：{"errcode":268488001,"errmsg":"system busy, please try later rid: 64f7fdf1-52b4ea72-67f873a6"}

试了几次都不行，请问是什么原因