Disconnected from server. Machine FQDN %1 (IP address: %2, TCP listening port: %3, Type: %4) in pool %5 Cause: If the specified ...

Disconnected from server.

Machine FQDN %1 (IP address: %2, TCP listening port: %3, Type: %4) in pool %5
Cause: If the specified server is removed from the topology or is currently draining or is stopped, this behavior is expected; otherwise, a network issue may have caused the disconnect.
Resolution:
If this behavior is unexpected, resolve the network issues between the two servers. Ensure that the service is listening on the specified port and FQDN.