Buritto, a great deal of people are still experiencing the problem you appear to have resolved, can you copy the email or msg or screen grab, of the parameters you had to change to overcome calls not ringing through? I have searched for "router sip" and read the following link that explains why calls do not ring through for the ALG router they are discussing:
http://www.voip-info.org/wiki/view/Routers+SIP+ALG:
Perhaps, this may help as well and was the remedy:
http://voicent.com/predictive-dialer/bl ... rs-sip-algThank you.