I have a SIP trunk between Issabel and another propriety PBX. When calls to/from that PBX were forwarded to Issabel, it works just fine if the forwarded calls were picked up first by extensions in Issabel before it was released/hung up from the PBX. However, if the calls were not picked up first and simply hung up, the calls will still go through but the party on the other side cannot hear anything while the party on Issabel can hear just fine.
I have tried putting in progressinband=yes and also faxdetect=yes as suggested in other forums but still no go.
Appreciate any assistance.
