I’ve tried multiple variations of this page - One with the Authenticate ID being the same as the SIP User ID and currently trying it without it. I’ve tried both the UCP password and the secret. Used the hostname and the IP for it, the SIP Server.
Because the phone is incorrectly attempting to register to the chan_sip bind port.
In Asterisk SIP Settings, chan_pjsip tab, look for a section probably called 0.0.0.0 (udp) .
Check the value of Port to Listen On .
In the phone settings, the value of SIP Server should be the host name or IP address, followed by a colon and the port number you saw for Port to Listen On. For example, sip.example.com.au:5160
Of course, use the actual host name or IP address of your PBX, and the actual value of Port to Listen On.
If you still have trouble, post what now appears in the Asterisk log when it attempts to register.