Unable to register sip truck but xlite can!

I am trying to register my asterisk to my sip provider.

Have been reading various different sip provider examples but none seems to be able to work.

I have been getting message like
Got SIP response 423 “Interval Too Brief” back from XXX.XXX.XXX.XXX
chan_sip.c: – Registration for 'XXXXXXX@voip.XXX.com’ timed out, trying again

I tried with xlite with keying in
username / password / server and it will work.

Is it possible to extract the correct outgoing string and registration string from xlite?

Please assist. Tks a million!

All right I have made some progress but no solution.

I manage to register sip truck to my provider. I confirmed by checking the log registration.

Problem:

  1. I still cannot make outgoing call. Operator will say busy.
  2. I can receive incoming call. BUT when answer, it hang up.

What might be the possibilities for such problem?

Xlite client has no problem when connecting direct to provider.

Any advice is appreciated.