What changed between 1.20.6 and 1.21.1 that keeps structures from generating for me?

I have an old datapack that I wote in 1.20.6, it was a failed pack where I tried to make a biospheres datapack, now I want to revisit it, but when I load the pack up, and go to the dimension that is suppose to only be is just a empty space with some floating structures, the structures simply doesn't generate. They can be located, but it only generates air, while in 1.20.6 it works just fine. I looked at the console, and there was, no error, no warning, nothing... I really have no idea what could be causing this. Is there a know bug or something? Here is the structure json: { "type": "minecraft:jigsaw", "biomes": "biosphere:biosphere", "step": "underground_structures", "spawn_overrides": {}, "terrain_adaptation": "none", "start_pool": "biosphere:spheres", "size": 6, "start_height": { "type": "minecraft:uniform", "min_inclusive": { "absolute": 0 }, "max_inclusive": { "absolute": 200 } }, "max_distance_from_center": 80, "use_expansion_hack": false } strucutre set: { "structures": [ { "structure": "biosphere:spheres", "weight": 1 } ], "placement": { "type": "minecraft:random_spread", "salt": 561107275, "frequency": 1, "spread_type": "linear", "spacing": 5, "separation": 3 } }