I checked the fax logs for the 17th and don't see any incoming calls to your fax number logged. We'd see an inbound call even if no fax was sent. I dialed your fax number this afternoon and heard the fax tone and then saw corresponding log entries showing I called your number even though I hung up.
If they still can't fax you, this might mean there is something else going on preventing them from reaching us since we don't see anything inbound to your number.
Would you mind sending me a private message on the forums, or emailing email@example.com
with attention to me and include the phone numbers they may have been faxing from so I can take a look based on the incoming numbers?