If you have renamed HyperV Hostname and Veeam cannot connect to enumerate the VMs running, use this script to change the hostname of the HyperVisor:
Asnp VeeamPSSnapin $server = Get-VBRServer | ?{$_.name -eq "IpOfVC"} $server.SetName("NewIP")
This will rename the host from the existing in Veeam to the new one you have set. No reboot required.