Registration Failed Error/Provider Error

[lookingforfood]

I am having a small issue with my initial configuration. I've successfully configured new fies to function using Flowroute and Google voice, however the provider that I am trying to ultimately use (RingCentral) I am having issues with.

I am not sure if this is a result of how I am configuring my SIP Profile or if the provider simply won't allow me to authenticate. The errors I receive have been "Registration failed with status service Unavailable 503" along with others depending on my configuration.

The values I am provided my ring central are: SIP Server, Outbound Proxy, a User name/Password and an "Authorization ID". Is there a recommended way for configuring for all these fields? Would my configuration resemble something like this:

<gateway name="sip server"
<param name="username" value="username"/>
<param name="password" values="password"/>
<param name="outbound-proxy" value="outboundproxy"/>

I've successfully used this provider with similar technologies (Voicent) who provided me with the option to include an Authorization ID, I feel like it is a minor configuration issues on my end. Is there any way to explicitly provide the Authorization ID?