Entities not spawning in custom grass blocks

Hi! I have a problem:

Entities of the creature category (custom and vanilla) doesnt spawn in my custom blocks. They are categorized as "Grass" in material. I also tried the "Earth" category.

(Its a problem with the blocks, beacause when I changed the custom blocks with vanilla grass blocks the creatures spawned)

What should I do?? Maybe its something with tags??? Thanks in advance!