Cub Cadet LT1042 blades won't engage

Mower cranks/runs fine, but blades won't turn/engage. I here a click when I pull the PTO switch out. I get 12 volts all the way to the PTO clutch. What can it be? I'm a DYI guy. Not a mechanic.

Cub Cadet LT1042 blades won't engage