A recent update to MalwareBytes is incorrectly blocking access to Fantasy Grounds. Symptoms are an inability to Join Game as a player or to Host a game as a DM (i.e. Failed Connection Test) even after setting up the port forward for port 1802 TCP as described on https://www.portforward.com.
We have reported the issue to MalwareBytes and they've confirmed that it is getting blocked within their Web Protection feature. They have not given us an ETA on resolving this but we will keep you posted as soon as they let us know.