Ensure that the Windows Remote Management (WS-Management) service and the VMM agent are installed and running and that a ...

Ensure that the Windows Remote Management (WS-Management) service and the VMM agent are installed and running and that a firewall is not blocking HTTPS traffic. 

This can also happen due to DNS issues. Try and see if the server (%ServerName;) is reachable over the network and can be looked up in DNS. You can ping the virtualization server from VMM management server and make sure that the IP address returned matches the IP address locally obtained from the virtualization server. 

If the error still persists, restart the virtualization server, and then try the operation again.