Hello Mel, What might be happening is that you are using either pokemon from different egg groups or pokemon that are the same gender. If this is the case the apple will not show up. In order to successfully breed 2 pokemon, they must be in the same egg group, and you can easily google which egg groups your pokemon are in. Furthermore, please check their genders to make sure they are opposite! i hope this helps, if you have any more questions feel free to message me on discord or on the forums.