Certificate "Not Trusted" on iPhone

Hi,

I have a Mac mini running El Capitan server. I configured RADIUS so I can use WPA2-Enterprise. I bought a SSL Certificate from Network Solutions AND created an A-Record pointing to my server at home (server.example.com > 24.X.XX.XXX).

When I connect to the SSID (WPA2-Enterprise configured), I entered my credentials, the certificate displays "Not Trusted" in red. I then click Trust and I'm connected.

Is "Not Trusted" displaying in the certificate is normal? If not, how can I get the certificate display "Trusted" in green?