I don't have a fix for faxing or an explanation for the sudden problem, but we ruled out networking as an issue. We ran multiple tests with ISP and Wireshark. Confirmed minimal jitter, 0 packet loss, sub 10ms return times, etc. Port settings all line up and no filtered/blocked traffic. Apparently we have ATA that won't communicate like it should. ISP says this happens with other businesses and offered to provide analog lines instead (more consistent). We're going to test online fax service first though. Thanks for the comments on the sanity check.
... View more