Farming and Agriculture - JD 425 front hitch up down won't work??

I own a 1996 John Deere 425. I know nothing about tractors and purchased a front hitch for it this summer off e-bay. I had it hooked up by a friend of mine from work who also changed the oil, spark plugs and fuel filter for me at the same time. I attached the hydraulic coupler kit and angle kit myself. I put the blade on it. I also changed the transmission oil and filter. It used nearly 2 gals. The hydraulic didn't work. So, I realized we forgot to install the hydraulic valve when we installed the front hitch. I just installed the valve and the angle works as the blade goes back and forth but the up down does not work. The transmission oil gauge shows enough oil. What am I doing wrong?

The oil gauge doesn't show the volume, just pressure. You can have enough pressure to move it laterally, but once the pump has to fill the cylinders it balks. How much does the sump hold? 2 gallons seems a little shy. You are filling up a tractor, not a lawn mower, so find out how much is needed. Does it have a dipstick? If so, check the fluid level with all the equipment at rest, or extended.

The dip stick does show enough transmission oil on it after I've moved the tractor back and forth a couple of times and then let it sit for 10 min. This tractor has only had a mower deck on it so it's never had to use the lower lever.

I'm not sure if I totally understand:o .... . but if the rear lift works and the front doesn't and it's like my old ford tractor, there is a valve that switches the hydraulic from the front lift to the back lift. You can work one or the other but not both at the same time.

On mine the hydraulic fluid is checked with both lifts fully extended.