Hi Peter W Zheng,
1. Where do the client update from, from Microsoft Update or WSUS server?
2. Is there any proxy between the client and Update Server, the error is generally due to incorrect proxy settings;
3. If there any firewall between the client and the Update Server, if you are using WSUS 4.0, please ensure http port 8530 and https port 8531 is opened.
Best Regards,
Anne
Please remember to mark the replies as answers if they help.
If you have feedback for TechNet Subscriber Support, contact
tnmff@microsoft.com.