Why is the Windows Update fail


When the device is used in Trusted NW (ZCC ZIA OFF), Windows Update fails.
However, there is no evidence of blocking in the ZIA logs (Web & FW).
When using UnTrusted NW (ZCC ZIA ON), Windows Update succeeds.
The Trusted NW uses Cisco SD-WAN, but no access control is set for Windows Update.
CiscoRouter and Zscaler are connected via IP-SecVPN.

Could you please tell me why Windows Update failed?

This is happening on all devices and the OS is Windows 10.