Baking is a science. If your baked product in the air fryer is not soft and fudgy or does not rise properly, then in that case, there might be several reasons. You need to preheat the air fryer properly, if your air fryer is not hot enough to bake the muffins it will be failed to increase nicely. Secondly, if the banana muffin batter is overmixed or undermixed, then it will give you a disappointing result. So just mix them until all the ingredients will be combined. If you open the air fryer basket multiple times at the time of baking, then the air fryer will lose heat and will be resulting in an uneven, flat surface muffin. Always mix the baking powder and baking soda in the batter at the last moment when everything is ready to bake.