Nagios Support Forum

It looks like you can get that response from a host running nsclient and check_service isn't in the nsclient config...

Looks like the plugin wants args in some order. This from the short help output I read...
command[check_tcp]=/usr/local/nagios/libexec/check_tcp $ARG1$ -w 10 -c 20

Try adding $ARG1$ to the command.
command[check_tcp]=/usr/local/nagios/libexec/check_tcp -w 10 -c 20 $ARG1$

You need a nagios command. Services run commands, and commands run plugins.

Maybe kill the ncpa service processes and rerun the upgrade.

Use curl or wget to fetch the upgrade check URL.

Probably need to see why ndo3 isn't running, why it isn't responding.

https://www.google.com/search?q=NDO-3%3A+mysql_ping%3A+Unknown+error.+Is+the+database+running%3F&sca_esv=902f5ec581767639&hl=en&source=hp&ei=3dT1ZbSjGbHe0PEP5_SR2Ao&iflsig=ANes7DEAAAAAZfXi7aDD8zPuR1cy6yj2lY5hgcO8o6gs&ved=0ahUKEwj0hb66pfmEAxUxLzQIHWd6BKsQ4dUDCA4&uact=5&...

I think nagvis just uses the standard httpd config.
https://httpd.apache.org/docs/2.4/howto/auth.html

Might want to check host/IP resolution and look at the ES log file.