I believe the default port is 8080 not 18080. Give it a try.

Phones automatically register with SIP server if you assign SIP Server address in phone's configuration.

Just shut down the phone or maybe there is some options inside the phone allow you to set when to connect to SIP Server.

When you click on "Registered Clients", how many are there? If there are already 10 users, then you won't be able to register new user any more.

PAL sounds like an interesting control, has anyone used it yet? I don't see any post about it yet. How does it work?