I could use some help please, if anyone can figure this out. I am an experienced with sewing machines but I now own my first serger. I was doing fine. Sewing along with great results when suddenly the serger was not locking in stitches anymore. All I get is 4 strands of thread, no stitches at all. I have read the manual, checked all the insides to make sure everything is still threaded and done correctly, changed both needles and checked the settings on the machine. I just got this machine for christmas last year and began using it this month...any ideas what is wrong? anyone?

Thanks for reading, Lynn