'The application cannot communicate with the ESX/vCenter server.Verify that the server is online and available.'
Below error would be observed in the ARCAPP.log
[ERROR]getDiscoveryEsxServerscom.ca.arcserve.edge.app.base.serviceexception.EdgeServiceFault:The network adapter on the source computer is not functioning properly.
Discovery of nodes from VMware vCenter in ARCserve Central Host-Based VM Backup might fail with the above error.
We will need to make sure that 'VMware VirtualCenter Server' is started in the VMware vCenter server, for detailed steps please refer the below VMware Knowledge Base article: