IAX Trunk working/not working

We are reworking our Freepbx server and are going to VM it. The current version is (PBX in a Flash) with asterisk The new version is (FreePBX Distro) 12.0.74 with asterisk 11.17.1. All the IAX trunks to our remote offices are working fine except for one. With our old pbx server, the main office trunk will connect to the remote office (shows status OK), but the remote office is not connecting to our main office (shows UNREACHABLE). In the new pbx server, the IAX main office trunk can not establish a connection to the remote office, but the remote office can connect to the new pbx server. The remote office is using the same version as our old system here (PBX in a Flash) with asterisk I have checked the trunk settings and even copied them from trunk to trunk but still the same results. Any suggestions on what might be wrong?

Thank You

Do you feel like this could be a networking issue independent of the PBX, or that the issue is on the box itself? Have you checked iptables and the like?