Have you disengaged the clutch? is the needle going up and down at the same time. If needle is still moving, then clutch is not disenaged. This is usually a knob inside the flywheel, or a button on the flywheel, machines will vary. Just recheck your manual and ensure that you have disenaged the drive to the needle.
Now check that the bobbin winder is engaged. On most machines, you need to move the bobbin and the spindle it sits on over against a stop to engage the bobbin winding mechanism on top of the machine.
If you have done all this and the bobbin just isn't turning on the spindle at all, then it may be the rubber ring just inside the case which drives against the flywheel, has worn out. Proper name is "Bobbin Winder Tyre".
This is a link to the part I mean
http://www.sewingpartsonline.com/bobbin-winder-tire-brother-x55238051.aspx there is no image but they look like a little black rubber ring and being rubber, they do wear, perish and crack with age.
So if you are able to open up the machine covers you may well be able to see this part and replace it yourself. Or just confirm the diagnosis. They are not expensive to replace.