My Bernina only straight stiches

Question

I have a Bernina Bernette 66 and I was making some Pj bottoms and needed to sew the elastic together with a zigzag stitch which worked fine the first time but a day or so later when I was finishing the other pair it wouldn't work. The plain black stitches work fine but the ones with the stretch stitch with it won't work. Then when you try to do the plain stitch it goes backwards. I read the manual made sure it wasn't on the Stretch one, took all the threads out rethreaded the machine. Went through all the stitches again and nothing. I have talked to two really good seamstresses and also got nothing and it is going to take over a week for a tech to look at it Please help!!