There are a couple of methods to remove a stuck shower drain. Drains generally become stuck because of grime and scum build-up, or because it has become scaled. Throw a handful of baking soda down the drain and add hot water; it should shift whatever is seizing the drain.
You can also try pouring neat white vinegar down the drain. The other way to unstick the drain is to spray lubricant and then twist the strainer with long-nosed pliers.