MF 240 4x4 3 point wont raise

I have a MF 240 and the 3 point is unresponsive to either lever or both raised. Tractor has two remotes and both work so pump is pumping. 3 point suddenly stopped working. It lowered but won't raise. Rock shaft moves freely by hand. There is no noise from hydraulic system except when remotes operate.
Any pointers on where to look would be appreciated.

UPDATE:
Finally had a chance to mess with the tractor. the lever hanging down from the top moves forward and rearward when the draft and position levers are moved. With the engine off the roller follows the linkage. As as the engine is started the roller moves all the way forward away from the link. Moving it rearward manually has no effect. It pops back to the front as soon as it is released and has a good bit of pressure making it go back. I did notice as soon as the engine starts the lift arms raise a couple inches then drop back down. That is the only movement seen. I was able to see the lift cylinder. There is a pretty good stream of oil pouring off the cylinder. Most seems to be coming out of a 3/8" (8mm) or so hole. Doesn't make a lot of sense that the valve moves freely until the engine starts and then snaps forward.
Does the top cover need to come off? Check out the cylinder for damage? Is relieve stuck? Is there an O-ring wiped out on the valve causing the spool to snap forward? Any further pointers appreciated before I dig deeper.

I'd hazard a guess, and say that the suction filter is choked.
Remove it and don't even bother trying to clean it, just bin it and get a new one. It's obviously "pretty bad".

What is happening on start-up, is that the control valve is being sucked into the lower position, because the pump cannot draw enough oil thru the filter.
Let us know how you go,
regards, Evan.

The filter was completely clogged with metal shavings. Reusable metal filter so cleaned it out in parts washer and 3 point happy now. I don't know the history of the tractor. By the amount of metal in the oil it either had a serious bearing failure or is about to. Nothing makes odd noises but something is or has been chewing up the metal. Time will tell.

Thanks for the pointer. Expected something serious since it just quit working and wasn't a gradual issue.