Rethread, change the needles, clean away any lint or whatever around the loopers.....but me thinks if nothing else the timing could have gone out....which means a repair shop unfortunately. You might wait and go get a book at the library which can help you with minor repairs...seeing as the stitch isn't forming I'm hoping it is just the threading gone haywire.

It sounds like a lower looper is not threaded correctly. Follow Budster's advise about re-threading etc and I bet you'll be sewing again in no time.

when you say it wont stitich do you mean: 1 the parts dont move or 2. they move and don't make stitches?

If it's the latter, check, recheck, and check again your threading. the tiniest thing can mess up stitch formation.

My new serger has a safety switch, and won't go at all if all the little doors aren't closed all the way.

The parts move just fine - they just don't loop to make stitches. There's no damage to any of the moving parts I can seen. I've checked and rechecked the threading. When I try to stitch fabric the thread comes off the spools just as if it was actually working.

That comment about timing is interesting.

And it says if stitches aren't forming...check for bent needle, Needle not inserted correctly, Incorrectly threaded, Sewing foot pressure too weak (in which case you inscrease sewing foot pressure) and lastly incorrect seting of thread tensions. I did have a book out from my local library....look for it and perhaps it can help you.."The Ultimate Serger Answer Guide" by Naomi Baker, Gail Brown and Cindy Kacynski - IMHO it sounds like some timing is out somewhere...it might need some professional adjustment.

often with a serger we think we have checked the threading and the tiniest thing can mess it all up.

so start all over with the manual, replace the needle, make sure you are engaged in the tension disks and that you have done everything in the proper sequence.

All that failing, shout for the repair person. Isn't that a total drag?

When mine won't work, I take out all the threads and re-thread in the order that the manual calls for. So far it always works. How that dratted thing can tell if I thread the needle before a looper I have no idea, but it can.

I spent several hours tinkering with it last night and this morning. I replaced needles (the old ones were ok), rethreaded everything according to the manual using different color threads to check tensions and such. It actually stitched/sewed about 6 inches before quitting again. Whatever the problem is it's in the loopers. The needles stitch as they should but there's nothing happening with the lower threads. I've played with tension, stitch length, etc. It's not doing a thing. Thinking back, it messed up in the middle of a stitch and hasn't been the same since. So maybe it did jump timing. I'm leaving for a few days next week and was planning to take my other machine in for service. Looks like I'll have to take both. :(

Here is a tutorial on how to fix the timing

Here is a link that might be useful: serger repair info