Hi Please would anyone help point me in the right direction with a problem I am having on FreeSWITCH (Version 1.8.5 -6-31281a0bf1 64bit) on FusionPBX I have FS connected to Cisco Call Manager over a SIP trunk (insecure) and remote endpoints registering over the internet to FS secured with TLS and SRTP <CUCM PBX> --- [SIP Trunk TCP + RTP] --- <FS> --- <FW/NAT> --- [TLS Registration + SRTP] --- <FW/NAT> --- <Endpoint> I can make calls in all directions with audio, problem is when I try to do an transfer from a phone on CUCM to the endpoint registered on FS the call drops. Here is the capture https://pastebin.freeswitch.org/view/214d3b21 In this example it was a consultative transfer, the initial inbound call was answered OK, but when the transfer was initiated the call dropped. My understanding of the issue from analysing this trace is when the call is transferred CUCM sends a re-invite to put the call on hold maybe, that causes the following problems: Line 1546 2019-06-05 15:33:30.169172 [WARNING] switch_core_media.c:4877 RFC2543 from March 1999 called; They want their 0.0.0.0 hold method back..... Line 1587 2019-06-05 15:33:30.429173 [WARNING] switch_core_media.c:5551 Crypto not negotiated but required. Line 1590 2019-06-05 15:33:30.429173 [DEBUG] sofia.c:8216 Reinvite resulted in codec negotiation failure. I have exhausted my limited knowledge of what is going wrong and how to fix this and would be very grateful of assistance. Thanks Steve