Take the pressure line off where it goes into the valve or into te tractors transmission usually theres a 3 bolt flat fitting. See if its getting any flow. If not and the pump isnt squalling like it starving. I went through this on my YM3000. What happened on mine water got in the transmission from a leaky shifter boot. One night it was 14 and I started the tractor. THe lift didnt work after that. What happened the pump shaft snapped off. I figured the pump had frozen and when I started it just snapped. I had to buy a replacement at Hoyetractor for 400.
Does the powersteering still work if its euipped. Im not familiar with your tractor. Also the suction screen could be plugged.