Which (e.g., 7.0, 8.0) are you deploying?
You cannot download the Witness as a standalone ISO file from the main "Product Downloads" tab. It is located inside the vSphere ISO package. download vsan witness appliance
When upgrading your main environment using vSphere Lifecycle Manager (vLCM), always include the vSAN Witness host in your remediation schedule to keep build numbers identical. Which (e