I don't have your machine but here are a few things to try. Please excuse me if you already know to have tried some of them but I'll start at the basics since I don't know you. Rethread your whole machine, including using a different bobbin,(sometimes they don't get wound right) check the bobbin area to make sure it's clean of fuzz and also that the black part that holds bobbin is in correctly; mine was off a little once and caused all types of problems. I couldn't figure it out and then I took it out and redid it and it worked. You should also change your needle to make sure it good and it all the way. All of these things can affect it. Normally when the thread problem is under the fabric it's the top thread and if it's on top of the fabric it's the bobbin thread. Since yours is under the plate it could be either or a combination. I hope this helps and gets you back on the road to sewing quickly.