Exactly wat the man said.
open the hood and you will see the cable near the top of the firewall.
Follow it down to the deck.
It should be anchored at both ends.
Move the PTO lever a few times to see if the cable is broken.
From the anchor on the deck it goes to a spring which pulls against the tensioning pulley which pulls against the belt and the brake blocks.
Generally no resistance to moving the lever will be a broken cable.
If the belt has popped off or a pulley dropped off there will usually be some resistance as you are pulling against the return spring & blade brakes.
