Do You have a manual ? These have a 2 stage clutch & to engage the PTO You will need to depress the clutch all the way down to the foot step then put the lever in the PTO mode & release clutch & it should start to rotate & have the tractor in the gear you want don't try to shift while the PTO is engaged! Or You could break a shifter fork & don't try to shift from a forward gear to reverse while the PTO is engaged or you will break a shifter fork for sure as I did Stop the tractor completely & disengage the PTO & then proceed. Hope this was some what helpful.