The free wheel clutch / sprag is applied in 1 and R , slipping will cause no motion.

One of the friction elements is remaining applied, this is why the motor is against the torque converter / car won't move. Drag race cars apply 2 elements so the motor can be brought against the converter then one is released launching the car.

As a quick guess I'd say that B1 is remaining applied but that might not be true since 3 rd supposedly works. I'd want the car wheels to be elevated and see if 4 th can be engaged.