Userscripts.org

in Chrome F12, Simp. Chinese will got the following result:

> document.documentElement.getAttribute("lang");
"zh"

but in your script, the flag is 'cn':
> "cn": { // http://userscripts.org/users/349372
> errormsg: "错误：由于YouTube网站已更新，YouTube视频下载插件已与YouTube不兼容。",
> errorlink: "查看新版请点击这里。",
> ....

please fix this, thanks~

Confirmed. I've fixed it in my copy of this script. For any users that want to fix this problem while awaiting an official update, you can download the script with this fix included here.