It could also be the type of stitch you're doing. Invisible thread is really kind of fussy to use.

You have to loosen the top tension a bit and be sure to use regular bobbin thread in the bobbin not the invisible thread. good luck1 A little nylon "sock/net" can also help. slip it over the spool with invisible thread and just sew like that.

I have used it a couple of times, using most of the tips above. I was able to use it, but I don't usually use it. I have been sticking to matching cotton or poly thread, as I have overall better results. If the thread breaks after the item is sewn, the thread tends to start coming out on its own.