If it can be seen that anything is working (acces to port, authentication etc.) and an ICMP 'Ping' fails then it's assumed that ICMP is being blocked.

The RRPS may not be forwarding authentication requests for the realm in question

If there are signs of life from the RADIUS port but no response to auth attempts then it's assumed that there's a bad shared secret or the NRPS is an unknown client. Either way there's something wrong with the configuration.

If there are signs of life from the RADIUS port but no response to auth attempts then it's assumed that there's a bad shared secret or the NRPS is an unknown client. Either way there's something wrong with the configuration.

In the NRPS logs there are entries which show that the RADIUS server is attempting to communicate but has the wrong shared secret (or, much less likely, the wrong Message-Authenticator).

If the server is alive and the port looks like it's open but there's not response to RADIUS authenication requests then it's possible that the port is set to DROP.

There are limited checks that can be done for Visited Only sites. If there's no response of any sort then it's assumed that either the host is down or the NRPS are firewalled from making incoming connections.

There are limited checks that can be done for Visited Only sites. If there's no response of any sort then it's assumed that either the host is down or the NRPS are firewalled from making incoming connections.

For Full sites a host would be flagged as down if it also failed other checks. Basically if nothing worked then it's assumed that the host is down.

It's possible that there a problem with the network path between NRPS and this RADIUS server. Check the DNS, the IP address and the routing.

If there's sign of life (ICMP works) but there's no response from any of the RADIUS checks then it'll be assumed that the daemon is down.

If the server is alive but the port is tested as closed then a firewall might be set to REJECT.

If there are responses to authentication requests but the RADIUS port appears closed then it's possible that an IPS is stopping the port test.

If Status Server is supposed to be configured then tests will be performed. A lack of response means that it's not actually configured properly.

The authentication is attempted and a negative response received, which implies that there is a problem with the test account (non-existant, expired etc.)

The site's IdP(s) might not be suitably configured to authenticate for the realm in question.

The ORPS may not be proxying authentication requests for the realm in question.

Currently it looks like nothing is responding so it could just be that nothing has been configured yet.

Authentication requests going to your site aren't being responded to, thus your site is being marked as down by the NRPS. This could be down to local configuration, or the configuration of a site proxying through yours.