The picture depicts a coil with a DIN connector. Should be held on by the red cap.
Under the cap will be a cartridge valve screwed into the valve block.
You won't get anywhere without identifying the manufacturer and part number.

The wiring looks hokey going to the coil, I would check that first.

You can take a small screwdriver, nail or something similar and lightly hold it near the coil while you simultaneously active the controls.
It the coil and circuit is working, it should draw the metal piece to it.