我使用下面的REST调用从WMS获取访问令牌，问题是，有时它有效它会产生错误"A server with the specified hostname could not be found"，一切都相同但输出是随机的，为什么会发生这种情况？我正在使用c＃console项目来发出此请求。
POST https://wamsprodglobal001acs.accesscontrol.windows.net/v2/OAuth2-13 HTTP/1.1
Content-Type: application/x-www-form-urlencoded
Host: wamsprodglobal001acs.accesscontrol.windows.net
Content-Length: 120
Expect: 100-continue
Connection: Keep-Alive
Accept: application/json
Body:grant_type=client_credentials&client_id=ams_account_name&client_secret=URL_encoded_ams_account_key&scope=urn%3aWindowsAzureMediaServices