The vCenter Server is not available and the vCenter Server VM needs to be restored.
In order to restore the vCenter Server you will need to add one of individual ESX(i) hosts to the Veeam console. This will allow Veeam to restore the VM directly to the host.
1. Add the standalone host:
2. Restore the vCenter VM to the standalone host:
(Be sure to choose the option to restore to a different location with different settings.)
Please try using an alternative way to contact the server. For example, if the name you tried to use was the IP address, try using the hostname. The hostname for a host can be found in a vSphere Client under Configuration>DNS & Routing.
Please be aware that starting from September 2018 downloading updates will require an active contract for the corresponding product.