As of now, all of the add-ons from the Minecraft Marketplace are completely broken. No matter the world, or even with experiments turned on, add-on blocks show up as "Unknown" grass textures, blocks and mobs don't even show in the inventory. Keep in mind that these add-ons are from the MARKETPLACE and that I PAID REAL LIFE MONEY for them. Seriously, this needs to be fixed ASAP! I have even tried clearing my cache, and completely uninstalling the packs from my game. I also checked for pack updates, which were none.