When I had that happen it was because the bobbin was threaded wrong. I have the Topaz 20 and when i put the bobbin thread in I cannot cut of the thread until the cover is back on, then a quick pull of the thread and it is cut. Also, I found my machine wants the top thread and bottom thread to match. It does not like the "bottom" thread when I do embroidery - it just looks horrid. So I use white embroidery thread underneath. Not a big deal for me.