And even after I disable IPtables, I still don't get anything showing up in the CLI.
Or is it probably something on the remote router or server?
if you disabled iptables and it didnt work then start looking at your router that the pbx is behind. It is probably blocking it.
last quick test to do is reboot the pbx (to clear any possible fail2ban lockouts) and as soon as it is booted up attempt to register the remote phone. If nothing in the logs then its probably the router blocking them from ever coming in.
Again assuming the permit field in extentions is properly setup along with travleing man.
your permit field says something like the following example but with your real ip (not your internal ip such as 192.168.1.0)
100.101.102.0/255.255.255.0
merlyn