Grandstream GPX2000 Multiple SIP Servers

I am working with a Granstream GPX2000, and two Asterisk Servers, and am having some issues.

Server 1: Trixbox
Server 2: Asterisk 1.6 running on CentOS

What I am trying to do is setup Line 1 to run on Server 1 and Line 4 on Server 2. I have all functionality working on Line 1, but I cannot manage to figure out why line 4 is not registering.

Server 2 is working, I have a DID configured and able to dial into it, I have dial plans that allow me to dial back out from the DID.

My SIP configuration:


My Extensions.conf (for outgoing context)

exten => _1NXXXXXXXXXX,1,Dial(SIP/${EXTEN:3}@TrunkProvider)

Can anyone give me some insite as to what I am doing wrong?