异常日志：#827 unionIdConvertExternalUserId:{"errcode":610023,"errmsg":"customer limit exhausted, hint: [1739435760128591151864936], from ip: 47.108.106.222, more info at https://open.work.weixin.qq.com/devtool/query?e=610023"}

企业微信API调用unionid_to_external_userid接口返回外部客户达到上线？但是外部客户数并没有到达上限。 请问是什么原因？