Thank you for looking at the wireshark files. I made the changes you suggested. In dm 5.2.18, I turned on sip trunk real ring back. In dm 5.2.13, I changed the options timer to 60 seconds, changed the hold mode to sendrecv and changed the codec preference to g711u first, and g729 last. And in dm 2.1.2, I made sure the system was set up for Private. I made test calls in and out of the system, with and without traffic on other lines and tested call hold on calls and all is working!

Thank you very much for all of your time and efforts, nameless. I really appreciate it!