Unable to register - setup problem?

[gnirtS]

Ive been trying to configure this software with my Voip provider but so far with no joy at all, after a second or 2 of "registering" it just falls back to "not registered".

The settings i have off my Voip provider are:

From their setup instructions it has:

In your phone's configuration menu there should be an option to define a SIP Server, SIP Registrar or SIP Domain value. Set the value to: voiptalk.org.

In order to do that ive set the "EXTERNAL SERVER" part of the 3cxphone to voiptalk.org

Then it states:

For SIP Authentication, set your SIP User ID or similar to your VoIPtalk ID (eg 84411076) and set SIP Password or similar to your six-digit VoIPtalk Password provided in your activation email.

So my username and password has been entered in the fields in the profile setup.

Next it has:

If you have an Outbound Proxy setting, set this to: nat.voiptalk.org:5065. Alternatively, if this setting allows you to define the port in a separate field, set the IP Address to: nat.voiptalk.org and the port number to: 5065.

So to configure that ive gone to profile > Advance and set "proxy" as nat.voiptalk.org" and "port" to 5065. I've also ticked the "Enable NAT" box

After doing that it fails to register, just goes back to "not registered". Ive tried it without "enable NAT" ticked and same problem. Ive deleted the STUN server and same problem.

Is there a log file being produced anywhere that i can read to see if/where its failing or can anyone help suggest what im doing wrong in the setup or missing out?