@maryamb99 - have you set the username and password before uac_req_send() -- see the attributes at:
The CSeq is incremented automatically when getting the 401/407.
I need something like $uac_req(method) which let me to assign new value to CSeq header of my new packet but it isn't defined in structure of uac module and I added this part in source of uac and tm modules according to my observations , always CSeq number is 10 in type of my requirements and my definitions , not incremental after receiving 401