I ASSume it operates like a New Model Blackhawk with the looks of an Old Model or a Colt SAA....?
Check the firing pin protrusion by dry firing it WITHOUT releasing the trigger. If there is too little protrusion check to make sure the transfer bar is up enough. If it is, the pin is too short, the TB is too thin, or the hammer's face notches are mis-cut.
Did you buy it new? If not, any chance some fly by night cut a few coils off the mainspring? Have you have the grips off to check for a commie-lock?
What is the air gap between the frame window rear face and the surface of the primer (what gap does the firing pin have to span)?
Finger placement can matter on a transfer bar single action when the timing is on the verge off being off AND there are clearance tolerances and run-outs adding up....could make a difference on getting the TB up far enough soon enough.
I'd call Taurus unless you like fiddling.
Pass the gravy.