FreePBX 14 + Fax Pro 14 = "The call dropped prematurely"

Hey guys. I’m hoping someone else here is using FreePBX 14/Fax Pro 14 and has it working so I can hopefully get this issue resolved.

The first issue we can into has been resolved as part of ticket FREEPBX-15273. Essentially, it didn’t even think the extension existed, so it wouldn’t even attempt a fax ‘call’. Unfortunately we didn’t get very far as now the call is made, T.38 negotiates properly, but we end up with “The call dropped prematurely.” We get this result when sending to a known working fax machine we have in our prod environment, and also when sending it to I worked with someone on the Flowroute Ops team (sent a fax to them directly even) and the end result was:

“We found the fax you sent & saw that it did connect, but no fax was transmitted from your fax machinen (FreePBX). The fax failed because it “timed out waiting for the first message”. This is going to be an issue within your fax system that is causing the faxes to not transmit to the destinations. Please review the logs of your fax system (FreePBX) to figure out why T.38 is being negotiated successfully, but the actual fax content is not being sent.”

So I just have two questions to start:
1 - Does anyone have fax working on FreePBX 14/Fax Pro 14?
2 - Is there anything obvious we are missing that would cause this?

Luckily this isn’t a showstopper for us because we barely care about fax, but it would be nice to have working before we go live. Thanks ahead of time guys.

I have it working over a non-t.38 connection.

False alarm. Our firewall was the culprit for our second issue.