Does your machine sew a locked stitch when you are regular sewing without a darning plate?? Are you using a darning foot with the 'plate'? Can you not drop the feed dogs instead and just use the darning foot? Have you ck'd to make sure the bobbin thread is unwinding in the right direction? Don't know what kind of machine you are using, but if you are using the darning foot, be sure to drop it just as you do with a regular sewing foot.