Im having the same issue and have a ticket open with support Sipstation and another thread here on this same issue. Support is saying exact same thing, my system is not responding…
Sangoma Asterisk Technician replied in my other thread and said Asterisk outbound faxing is indeed broken. He said it will be a few weeks before the Asterisk update that fixes this lands in FreePBX… Just an fyi. Here’s link to my thread with this same issue and his response…