Help with Needle and Plate

:confused: We have a Happy 1201 and have had to change the Rotor Hook and redid the timing - now after all that the needle started hitting the plate in the middle of a project. Please tell me what I need to do to fix this problem.

are you sure the needle plate is in correct position?
normal when the needle is down, must be in the center of needle plate hole.
do you use the right needle plate?
must be two needle plate: one for caps/tubular and one for flat