Apologies if this is a known issue, but I'm playing with the latest version, Bannor/Capria. I make Confessors to found temples in my own cities and rivals, but The Order doesn't spread to any of them. Also, even when I do spread the religion, I don't get any visibility in the city. It's been awhile, but I don't remember there being a civic requirement in FfH2.
Spreading religion is fixed in the upcomign versions. Religions no longer grant line of sight (this is a BtS chancge, though we may back it out for some of the religions).