[Freeswitch-users] Ricoh MP C2800 Fax SIP Registration

Hi, I have a Ricoh MP C2800 VOIP Fax that has VOIP capabilities. Unfortunately, the user interface is quite limited and it fails to register to FS. The SIP reply to the initial AUTH with the NONCE never gets back to the FAX. There is nowhere to specify external IP and PORT options so I have limited room to work on things on the FAX end. Does anyone have one of these working behind NAT? Any tips? I have tried NDLB options, but welcome suggestions. Thanks, Sean