Custom mob not spawning in custom biome

I am trying to make a mob in a custom biome, but the mob seems to not be spawning. I've looked EVERYWHERE, and can't find a single solution. None of them work. In the mob settings, I set it to spawn in the custom biome. I have it to where the mob attacks you, and can spawn during the day. Yes, I did have the spawning set to creature. Yes, the mob does spawn with a spawn egg. The Minecraft version is 1.18.2. The MCreator version is 2022.1.

UPDATE: I have changed it to ambient, but it only spawns in caves.

UPDATE 2: I've discovered it now only spawns at night, even with the creature spawning. Weird.