I'm trying to make a call from the system with Kamailio to a MS Teams. I can answer in the Teams client, system will receive response 200 OK and audio streams will be started.

The problem I have is that after a short period of time Teams sends BYE with the reason "An acknowledgement was not received for the call acceptance in the allotted time". If I try to hangup from the system side, Teams will receive BYE and respond with "481 Call Leg/Transaction Does Not Exist" - "Call leg unavailable".

It looks like Teams can not match and accept ACK request to finish establishing the call and the following requests have the same problem.

I was wondering if someone had this problem before or can share a SIP packet capture (of course with hidden addresses and domain names) of a correctly established and completed call to Teams?

Thanks a lot!

Regards, Volodymyr Ivanets