I see. Are you sure that FreePBX has WSS? I don’t see any mention of 8089 as a port in the Sangoma Firewall “Service Ports” list, and any Googling of “FreePBX WSS” suggested that it isn’t quite implemented yet, as seen in this post for example:
I can hold out a while for it though, or if you might know where to find the configuration steps I’ll give it a whirl.