Be sure to use an oven safe skillet or a cast iron skillet that does not have any plastic handles.
It's important to preheat the skillet on a stove top and preheat the oven as you need the correct hot temperature in order for the pancake to rise properly.
For maximum rising, it is best to use room temperature eggs and milk but I have made successful ones with cold eggs and milk straight from the fridge.
It's normal for the pancake to sink down at the center once you remove it from the oven.