Hello Benny, and everybody Happy to read again you !! ;-) I found sip provider that try to ask authenticate when it receive an Invite message but pjsip replies by Ack and not a new Invite with authentication information. Is it a bug in pjsip or server? Is it possible to follow this process, whereas the registration has been done ? Maybe I forgot to enable an option too. Currently: Client ---- Service Provider Invite --> <-- 100 Trying <-- 401 Unauthorized Ack --> Waited Client ---- Service Provider Invite --> <-- 100 Trying <-- 401 Unauthorized Invite --> Thanks Samuel