Trouble description: Ballast valve operator: Valve can be operated hydraulically by hand pump, but when we

Trouble description: Ballast valve operator: Valve can be operated hydraulically by hand pump, but when we tried to operate by wheel, the valve inside ballast tank is not moving.

Kindly guide me how to overhaul and what to check? What can be problem?

Measures taken: I have dismantled the wheel and top cover. Need guidance on how to proceed after this. If anybody has overhauled this ballast tank valve operator please guide me.

Present Status: Dismantled the actuator upto the point shown in the image.