SIP/2.0 407 Proxy Authentication Required
From Kolmisoft Wiki
The 407 Proxy Authentication Required response indicates that the phone must first authenticate itself with the proxy server. If received by the phone, the phone may repeat the INVITE request with a suitable Proxy-Authorization field. This field should contain the authentication information of the user agent for the next outbound proxy or gateway.
- Make sure username/password are correct
- Make sure you used username instead of user on far server (e.g. other Asterisk server) describing peer