Mine has done the same to me and it took me forever to figure it out. I had the needle threaded from left to right instead of right to left. I have another machine that threads the opposite direction and I get confused ( getting old). If it is threaded left to right it will not form stitches. Also, make sure your bobbin is inserted into the case correctly. The thread should be coming off the top of the bobbin towards you. When the thread is then pulled through the slot and under the tension spring, it will be as if folded back on itself. My FW will sew with the bobbin placed either way, but the stitches are much prettier if I do it right!