Try more. Seriously, torque converters are notoriously difficult to get seated all the way. There are several sets of splines, the pump notches, etc. that all have to line up for it to seat properly. Sometimes it helps to pull the converter out just enough that it isn't putting pressure on the splines/pump, turn 1/8 of an inch or so and try to push it back in. Do this until it seats. Unless you get lucky, this takes a while as you make your way to a 1/2 turn of the converter in 1/8" increments. Not a guarantee, but it usually works.
Good luck!