I have several machines, but only one (a Singer Quantum 2623) has the blasted needle threader. Needless to say, it is simply a waste of the plastic and metal used to make it. I have NOT EVER been able to get it to work, not by reading the manual and doing it step-by-step, not by guess and by golly. It just doesn't work (kind of like some kids I know!). Even the dealer I purchased it from couldn't make it work.
Some great gizmo they gave us, eh???