Is the 011 prefix accepted? According to
it should be 00.
If that’s not your issue, at the Asterisk command prompt type
sip set debug on
and make a test call. Look at the responses to your INVITE to see why the call was rejected. If you have trouble interpreting the SIP trace, post the relevant section of the Asterisk log at https://pastebin.freepbx.org and post the link here.