Perhaps you need to take it back to your dealer and actually sit down and sew with it in front of them so they can see what you are doing and what the problem is. Sometimes it's just something little that we are doing wrong. And once they "fix" it be sure to re-thread it and re-insert the bobbin and sew something with it before you take it home. It could just be a lemon that they don't want to exchange because of the cost to themselves.