Here is the issue we have when we are using google translate API, we have a key we bought, but when we accomplish the translation feature using the same code as the sample in this repo shows, we got https://content-translation.googleapis.com/static/proxy.html returns 404. This request is sent when we call gapi.client.language.translations.list
The error shows in browser's console is:

We tried REST API using our key, it worked well. So the problem we had here might not be the key?
So why we had the issue using this google-api-javascript-client? We got stuck here .
Any help please? Thanks in advance!
``
<html>
<head>
<script src="https://apis.google.com/js/api.js"></script>
<script>
function start() {
// Initializes the client with the API key and the Translate API.
gapi.client.init({
'apiKey': 'my key',
'discoveryDocs': ['https://www.googleapis.com/discovery/v1/apis/translate/v2/rest'],
}).then(function() {
// Executes an API request, and returns a Promise.
// The method namelanguage.translations.list` comes from the API discovery.
return gapi.client.language.translations.list({
q: 'hello world',
source: 'en',
target: 'de',
});
}).then(function(response) {
console.log(response.result.data.translations[0].translatedText);
}, function(reason) {
console.log('Error: ' + reason.result.error.message);
});
};
// Loads the JavaScript client library and invokes `start` afterwards.
gapi.load('client', start);
</script>