We just recently brought an Opt 81C online. We are cutting over our buildings one at a time. My problem is I can send and receive faxes between fax machines that are behind our pbx but I cant receive faxes from anyone outside our pbx. I can send faxes outside our pbx. We are connected to a SL-100 over PRI trunks. I can't seem to find anything in LD 10 to resolve the problem. Can it be the SL-100? Thanks for the help.