the previewConfig locale not work

const previewConfig = {
embedMode: "FULL_WINDOW", locale: "zh-CN"
}

document.addEventListener("adobe_dc_view_sdk.ready", function () {
var adobeDCView = new AdobeDC.View({clientId: "my clientid", divId: "adobe-dc-view"});
var previewFilePromise= adobeDCView.previewFile({
content: {location: {url: url}},
metaData: {fileName: "Bodea Brochure.pdf"}
}, previewConfig);

but the page tools not in chinse, it always in english.

By the way, is this usage free of charge? As long as it is an online calling method, regardless of what content is being operated on and how many users are accessing it