vCenter Server can report that the Primary VM of a vSphere Fault Tolerance virtual machine pair is powered off, but the Secondary VM is powered on.
After a failover occurs, vCenter Server might incorrectly report that the Primary VM is powered off and registered to its original host, and that the Secondary VM is powered on and registered to its original host.
This error occurs when vCenter Server is unable to communicate with the hosts on which the Primary VM and Secondary VM are actually running. vCenter Server reports these hosts as not responding and the problem persists until vCenter Server is able to communicate with the hosts.
To fix this problem, resolve the networking problem that is preventing vCenter Server from communicating with the hosts in the cluster.