Same thing happened to me. Here's how to fix it:

1- You gotta make sure the motor is at the "0" position. When it is, the 2 arms in the blue circle will be parallel to each other. If you didn't move the motor while uninstalling it, it should already be ok.

2- When you put the 2 parts together, the blade has to be like it is vertical in the windshield, in fully retracted position (green lines)

3- Then you rotate the blade to it's rest position (or "0" position, to match the motor). After that you can screw the shaft (red circle). The trick to find out where the 0 really is is to look where the arm gets fully retracted. Put the assembly on the car, the tip of the blade should be at 1.5" from the base of the windshield. If it isn't, take the whole thing out again, unscrew the shaft and re-index the blade. 1 spline will make a noticeable difference at the tip of the blade.