If the stabilizer picked up quite easily, the nut probably came off the end of the rod inside the cylinder. This is common. Take the hoses off the cylinder and install steel caps. Try to move the rod by hand. If it mover easily, that's your problem.
But, from the way you described, you hit the down lever and it went down normally. Up lever, and nothing. If the nut came off the rod, the piston would either be up at the top of the cylinder or cocked sideways. Either way, by hitting the down lever, it should not have gone down normally. But, being one side and not the other points to a cylinder. My vote is for something wrong inside the cylinder.