Remove the trackpad, being very careful not to scratch the screen.

Make sure all six washers are in place on the trackpad's screw posts.

If any washers are missing, check the magnet in the trackpad well—they may have gotten stuck to it when removing the trackpad.

Gently place the trackpad onto the screen so the screw posts line up with their cutouts and the edge with a ZIF connector is closest to the hinges