Hi,
First, please use DISM to check if there is any system file is corrupt.
https://support.microsoft.com/en-us/kb/947821
Did you use proxy to connect to the internet? Unsuitable configured proxy may cause this issue. Please connect to the server to the internet directly, then try again.
Besides, please check if there is any firewall block the traffic of windows update. Here is the firewall requirement of windows update:
https://technet.microsoft.com/en-us/library/bb693717.aspx
If issue persists, please reproduce the issue, then post the windowsupdate.log 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.