I have been using this serger for a few weeks now with no problems. Then I changed it from the 3 thread stitch I was using to a 4 thread again, putting 2 new needles on in the process. It wouldn't loop on the 4 stitch... so I tried the 3 stitch again, taking out the same needle I had before. Still no looping.
It is a Singer by the way. Could this be because I changed the needles? Did I do something wrong? Or did it kaput on me somehow?