Can you adjust the servo valve if it is set to manaul control?

Either the controller is not sending a +/- volt output or the control valve may have lost its +12 volt power or ground connection. There should be a 6pin weatherpack connector back at the servo. If it has a DJ servo then it needs the power and ground wires as well as increase/decrease to function. If it has a Raven standard valve servo then it just needs the increase/decrease wires.

Have you double checked your controller setup that it is still in liquid mode?