Identify and resolve reason for SIP Call Drop

FreePBX V[login to view URL] with Twillio SIP trunk using PJSIP driver. Calls drop after 30s, narrowed down to not receiving an ACK in response to initial OK after INVITE on incoming calls. Require diagnostic of the reason why the ACK is not being received (Twillio PCAP suggests that ACK is not being sent at all) Suspect issue is related to Contact Header IP not being using properly. Will provide remote access to Freepbx Gui, Commandline, and Twillio Console remotely. PCAP will be provided to suitable bidders. Needed ASAP on business critical line.