When I'm in the master rank my Pokemon don't get any hearts why is dat?

Because you probely stuffed up your pokemons stuff (the bitter sour thing) try getting scarfs. Eg. Max out your toguh and take to the Pokemon guy near the beach city and he will give you a tough scarf whihc boosts up your popularity

Your Pokemon probably doesn't get hearts because you probably did not give him any pokeblocks to boost up his/her cuteness, coolness, smartness, etc.

You need to feed your Pokemon PokeBlocks according to the Contest that they're entering. If you give them the best kind of blocks, including for the Nature they have, you will get the maximum amount of hearts possible, then the rest of the competition will be up to prefrence. Hopefully you have good moves for the contest. Best of luck to you.

You need to cheak their moves because if they don't match that contest you wont get any hearts.

If it's the part when you are showing your Pokemon and your's dosen't get any hearts and the others do it's because you have to give it poke blocks to raise it's condition such as beauty,cool,tough,smart,and cute which ever catigory you enter your Pokemon has to have it's condition up such as if your entering smart you have to have it's smart maxed out.And thats why you don't get any hearts.