I have several users, all at different locations, different firewalls. They all have one thing in common, they have AT&T Fiber for home internet. Seems that AT&T is blocking it. I use their credentials and I connect instantly. Even had one of the machines work w/o issue once they were off their home internet. That user called AT&T, said it seemed like they had a line of questioning and an option to enable the use of VPN for his account. They would not directly admit to it though.
have no issues hosting or connecting to vpns with att fiber…