No guest OS heartbeats are being received

When moving a VM, you might see this error message “Migration from <server.> No guest OS heartbeats are being received.  Either the guest OS is not responding or VMware tools is not configured properly.”

The tools have to re-establish their status to ESX, and then to the Virtual Center.  The warning won’t prevent migration, but you should probably wait long enough for the renegotiation to happen.