Creature does not spawn in costum biomes

Please someone find a solution to this situation. Even though it is not very nice, I designed special mobs with the help of a biome and geckolib. I want these mobs to spawn here, but this does not happen in any way. I tried all the methods, checked everywhere (all creatures) and searched all the forums. .I wanted to make more biomes and creatures in the future, but if this problem continues, it will never happen. If I have free time, I will post screenshots

I'm sorry, English is not my native language.