Tiger 800 Suspension

Last year U bought a 2013 Tiger 800 ABS...my 3rd Triumph & the first one with adjustable rear suspension. So the manual tells me to wind the preloaded screw fully clockwise then for solo riding turn it 15 clicks anti clockwise. Cant budge the screw with a screwdriver but I can get it to turn with a socket. Its quite stiff, but I turned it clock wise as far as it goes but it doesn't cluck when I wind it back. Is it working or is it seased up? Can I do anything with it? If it is still working ok but not clicking, how do I know how far to turn it back for solo riding?
Thanks, David