You have Windows Server 2008 with Hyper-V role. In VM configuration in Hyper-V manager, you have specified a static MAC address.
Backup of this VM fails with:
Error code: 1011
Message: Failed to obtain property 'AllowMacSpoofing'.
Issue in the product.
The issue has been fixed in Update 2 of Acronis Cyber Backup 12.5. Please update the product to the latest build.
As workaround, please install Agent for Windows/Linux inside the guest operating system of the VM; see details here.
The issue does not affect Windows Server 2008 R2.