If you haven't used them in a long time, oil may have hardened so the cams are not working. Try heating the cam area (with cam out) with a hairdryer, then try again. Also, tighten up your stitch length - they have to be pretty tight to get the look you are after. Practice on scraps the same thickness you will be using.
Finally, once you get your settings perfect, put a label on the cam with length and width settings so you'll know next time.