I don't use Torbirdy and have only even heard the name once before, but I had some trouble with enigmail myself for quite awhile. Updating to the latest Thunderbird & latest version of enigmail has everything working very smoothly now though -- this is on Linux, not Mac, BTW.One of the problems I had is that my gpg binary was in a non-standard location. Try setting the actual path to gpg in the PGP preferences (the enigmail preferences) in Thunderbird. Might work, might not. Also, run thunderbird in a terminal so you can actually see the output from it failing.