PTO is turning but the fly wheel is not, here's why. (New Holland baler) 

this will happen if those pins aren't oiled and sit for years. happens to all balers with this type of pto engagement. 68, 69, 268, 269, 273, 310 are just a few. when they went to the higher capacity balers they used a different type of engagement, on a 276, 277, 278, 320, 570 are a few.