Hello, everyone. I currently have a 3CX setup involving a couple internal and external extensions and am experiencing the following issue, dunno if some of you ran into this: When an internal extension calls an external extension, the call goes perfectly well. When an external extension calls an internal extension, the calls goes perfectly well... For 30 seconds only when it breaks. I pulled out a trace from the log and you can notice a message after 30+ seconds as per the below at 22:52:32.568: Code: 22:52:32.578 Call::Terminate [CM503008]: Call(27): Call is terminated 22:52:32.578 Call::Terminate [CM503008]: Call(27): Call is terminated 22:52:32.568 Call::Terminate [CM503008]: Call(27): Call is terminated 22:52:32.568 InviteADS::onAckNotReceived [CM503019]: Call(27): ACK is not received 22:52:00.482 CallCtrl::onLegConnected [CM503007]: Call(27): Device joined: sip:firstname.lastname@example.org:5060 22:52:00.482 CallCtrl::onLegConnected [CM503007]: Call(27): Device joined: sip:105@XXXXERASEDXXXX;transport=UDP 22:51:53.372 CallCtrl::onSelectRouteReq [CM503004]: Call(27): Calling: RingAll100:101Ext.101102Ext.102103Ext.103104Ext.104@[Dev:sip:email@example.com:5060, Dev:sip:102@XXXXERASEDXXXX:5060;transport=UDP, Dev:sip:firstname.lastname@example.org:5060, Dev:sip:email@example.com:12338] 22:51:53.362 CallCtrl::onIncomingCall [CM503001]: Call(27): Incoming call from Ext.105 to [sip:100@XXXXERASEDXXXX;user=phone] A weird 'ACK is not received' message is appearing and the call is terminated. Any way to fix this? Any help would be appreciated, Thanks. W.