So you're saying that you can push the PTO lever to "on", engine continues to run, but PTO does not turn?
Couple things. I have seen one mower that had excessive liquid gasket on the suction screen, which starved the charge pump, which stopped the PTO from working. If that's the case, warranty should pick up the tab on it.
But first thing's first. Look at your PTO shaft from the transmission to the deck gearbox first. See if you can turn it by hand. If it just freewheels, deck gearbox may have a problem. Or shaft itself may have an issue. You can actually raise the floor cover and look at the shaft while you're sitting in the seat, to know what's going on with it. Does it turn at all with PTO turned on? If no, then could be filter plugged with liquid gasket, could be internal problem, or could be real simple like a linkage issue.