Mowing NH 478 won't raise

[Jesselm78]

Have a 90's model 478 haybine... The mower is completely lowered and will not raise. The hydraulic arm moves fwd and back but stops dead when it hits the pivot arm. Tried raising while reved up, moving fwd and backwards and even went so far as to hook a chain to the pivot arm and pull it back with a bobcat. It seems as though the arm is ceased... Any ideas???