Pfaff 1471 will not re engage?

I took the stop wheel apart to fix another issue and when I put it back together it will be engaged, but when I turn the wheel backwoods and disengage the needle I cannot renengage it, the wheel does turn forward but no needle movement. Did I loose a spring or does it need oiling? The guts feel out so I wasn't sure how it was put together, but I believe I have it right. Any help would be great, thanks. I could provide a picture also. Thanks, Susan