A "cannot establish a connection to HOSTNAME" alarm is fired because of the connection failing to the host.
After testing the connection in "connection detail" by re-entering the credential. The connection works normally.
When using "Log in to the host using the same account used for monitoring Service" to setup OS monitoring, it creates a LocalCredential for OS monitoring, which is the FglAM login credentials, but not the "account used for monitoring Service".
Use option "Log into the host using different login credentials" to set the OS credential.