[Welsh Anorak]

Oh dear! Well, let's start with the obvious - is the belt on correctly? as you'll see, the FF is idler driven from the main pulley, and this is a belt driven slipping clutch. Not much else to it. However, do check the pulley for the counter belt isn't too tight. There isn't much torque available so the reel needs to be free to spin. Also check the brake isn't on. You'll soon have this spinning again.
That machine really does look in nice condition. As Peter says, reversing the pads should do the trick. As an aside, I think I have a spare degausser in the workshop. If you want to borrow it just ask, though it'll be around £3 to post.