Hi,
First, please make sure that the WSUS server can be accessed by the client.
We can use the portqry to check if the port used by WSUS has been blocked.
To download portqry, please click the link below,
http://www.microsoft.com/en-hk/download/details.aspx?id=24009
If issue persists, please post the windowsupdate.log of the WSUS client here. It may give some hints.
Best Regards,
Steven Lee Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Support, contact tnmff@microsoft.com.