The following might sound silly:
Check the position of the quadrant levers. Also check your fluid. If its milky, it means you have water in the system...could have frozen. If you oil looks like cake batter, drain it and replace it.
Aside from that, I would recommend referencing the OEM service manual and the I&T manual if you have access to one.
Also do you control the hitch linkage with a auxiliary hydraulic control box? If so, and this happened to me, the draft control lever must be up and the Position/Pressure Control lever in Constant Pumping.
If you have to change the oil, I recommend getting the oil from the Massey dealer. It costs a pretty penny (expect to pay around 150 for 8gal but the oil is a heavier viscosity than the TSC stuff.
I had the same problem when it was really cold around New Year's Day last month. Drained the oil and voila I have hydraulics again.