Pto willl not engage
Hi mate, Although my trade is repairing turfcare machinery, I have no experience with this model, so I will try my best. Firstly, the clicking you hear will probably be the electric clutch engaging/dissengaging. Firstly, see if you can get the clicking with engine off, keyswitch in first position/on/lights on dash. You may have to place something heavy on the seat and have traction pedal in neutral. MAKE SURE YOU DO NOT ENGAGE THE STARTER MOTOR/START THE ENGINE THROUGHT THIS!
Now have a look under the footwell on top of the deck and try to determine where the clicking is coming from, there will be a clutch there somewhere joining the engine drive pulley to a deck pulley, Also at this point check that both belts are on and with the ENGINE OFF! spin the blade/blades with your hand and ensure that the deck belts are not slipping on the deck pulleys. If they are you will need to establish where the tensioning system is. (Sorry i know pretty vague)
Back to the Clutch, once you establish where it is, engage the blades ENGINE OFF! and you should feel a greater resistance turning the blades as you are now turning the engine as well, beware though, it is theoretically possible to start the engine by doing this, but you will almost certainly not be able to spin the blades that quickly by hand.
If it is clicking to engage but not turning the engine pulley when spinning the blades by hand, then try tapping the clutch lightly as it may not be fully dissengaging.
I would put money on it being either one of the belts coming off/snapping, the blades jamming or the clutch not engaging fully.
If you find that the clicking is not the clutch engaging and its actually getting no power to the clutch then you need to go back to the pto switch and go through all safety switches! (good luck, it usually ends up with me bypassing them or running a new cable to the switch,then, smoke, shouting, swearing etc etc!) Either not advisable.
In doing all this you should have been able to have determined the problem be it one that I have mentioned or another.
Hope this helps,
Chris.