I took my sewing machine in for repairs once because it just wouldn't sew. The only thing wrong with it was that I had failed to return the lever that holds the bobbin onto the spindle after I had filled the bobbin. On that machine, the lever usually returns on its own when the bobbin is removed. That time, it didn't, and I failed to check. Lesson bought is usually well learned. You can be suse that's the first thing I check when there is any kind of a problem.