Pokedex unavailable on tablet

It's a little issue regarding the button active areas. I'm experiencing the same on iOs iPad air 2. Just tap on the lower edge and the pokedex will open normally.

yes, they moved the Tips bar/icon down so it is overlapping the Pokedex icon. Therefore, you have to press the bottom edge of Pokedex icon in order to work. You can tell if the Pokedex icon is properly pressed or not by observing the changing shade of icon.