What does VoIP error "407 Proxy Authentication Required" mean?

The "407 Proxy Authentication Required" message indicates the proxy is challenging the VoIP card for its authentication credentials.  The credentials, if correct, are provided by the Biamp VoIP device, and the registration process should automatically continue after the first instance of the error message.

However, if the error message appears repeatedly, the Biamp VoIP device trying to register is likely using the wrong Username or Password. Because the Biamp VoIP device will continue attempting the re-register, even with the wrong credential settings, the process can repeat continually without successfully registering. If this is the case, the Username and Password must be matched to the SIP extension configured in the proxy.