A test that we recommend to determine if you are having an issue with the DID card or the DID line is:
Find a manual fax machine and plug the DID card directly into the fax machine –
Fax something from the manual fax machine directly to the DID card by sending to your 4 digit numbers (or whatever your DID digits are)
If the DID cards are working properly you will see the C++ driver manager window appear on the FastFax processor that shows us receiving the fax. You should also see the fax from WRKFAXJOB in your inbound screen. If you see these things occur than the problem is with the phone line not the DID card.