Festive Mash-up Texture Pack Is Not Showing up When Applied to World

I was doing some festive pixel art and so wanted the Festive Mash-up texture pack on my world, I applied it as normal, but when I joined my world, it didn't show up, the textures remained the same. It was applied at the top level, though I tried it with and without other packs applied to the world. It shows applied in-game and out of game but the game textures are not affected.