Machine not sewing at all!!!

I bought a Brother CS 6000i and whether I use the bobbin lower thread method or the upper thread method (all completed according to the manual) I cannot get a single stitch. I have tried different threads, needles and fabrics. Everything seems to be working correctly and no weird motor sounds. The fabric feeds through nicely, the needle moves up and down, but the thread doesn't feed through unless I pull it through and a stitch doesn't form. Please help as I am getting very frustrated!