Is there a way to watch the needle come down and see if it's picking up the thread without the material under the foot? If it isn't completing the stitch then the timing may be out (to the shop for check-up) Things to try first: Have you put in a new needle? Is it the correct needle...too long or too short and it won't work. Have you changed to different thread in the bobbin and on the spool? Is the top tension so tight that the thread isn't advancing to allow the stitching? Some fabrics or quilt sandwiches are too stiff or tightly woven sometimes so you can get a skipped stitch. Change to different fabric scraps or sandwich sample and try it. That's all I can think of to try as I am not familiar with your machine. Good luck.