If you are actually hearing a good loud click or more like a clunk from the pto clutch,the clutch is working
In order for the clutch to spin the blades ..
1- Engine must be running..
2- The pto belt has to be on the pto clutch pulley..
Now b4 you think i am a smartazz,take the time to check these simple things that do get overlooked at times,especially over the age of 50.
If the fuse is blown,there will be no power at the pto clutch,no click is possible with no fuse.
The wires rite at the pto clutch are suspect
They often get damaged enough to still make the clunk but can't carry the load because of wiring damage.