If you don't have a female Ivysaur its image will not show That goes for all Pokémon. If you didn't have that gender before, it will not show up in the new Pokédex Up 0 Down
And I think it checks after a certain date, so even if you got one before it might not count. Up 0 Down
They should make it check dex when you feed a candy to one. So for example if you feed a candy to a female Blastoise it corrects the dex. Up 0 Down