Confirm that you created a pjsip extension and that Secret (set by you or automatically generated) matches what you entered in microsip for password.
If you changed Port to Listen On in SIP Settings, put that value after the server address and a colon, for example 192.168.1.123:5678 where 192.168.1.123 is the PBX local IP and 5678 is what you set for Port to Listen On.