Custom Mob Spawners Do Not Spawn Passive Mobs Underneath Platues (Or whatever there called) (Shown in Screenshot)

Okay, I used This code to spawn cows outside my base: /setblock ~ ~1 ~ minecraft:mob_spawner 0 replace {EntityId:Cow,SpawnPotentials:[

{Type:Cow,Weight:1}

]} but when I try it inside this structure... No passive mobs spawn... I changed the biome to and it didn't help at all... I don't understand why I can't do it in this area... I can do it in other areas without problems...