The only other thing I can think of is to thoroughly clean the bobbin area (remove the throat plate, too) and the discs. Make sure the foot lever is up when you thread the machine. Even if it is a brand new machine, some lint or thread piece may have gotten caught somewhere along the line.
Sorry you are having trouble. I love my Juki 2010. It is my "go to" machine for piecing and quilting. I really only use my Bernina 630 for embroidery and decorative stitches.