The plunger should slide out, fall out on it's own if held upside down.
That's how the mechanism works. Energize the coil and the plunger's steel bottom is pull up by the coil's magnetic force. The non-ferrous brass top shoots up and hits the cam on the gates axle to lower it.
If it's stuck, that's a problem. Pull it out, twist it, yank it, it's just a smooth rod. They you need to see why it's binding.