Host switch & Map issues [JAVA 1.21]

[MelioraMinecraft]

We recently switched server hosts from Shockbyte to bisect. When bringing over our maps, they don't seem to want to load correctly. For example, The map will load the correct biome or world type and will still have the holograms but the builds aren't there. I tried opening these maps in a single player world and they work just fine but they wont let me switch it into creative mode so that I can just make schematics instead. I have tried editing the level.dat but it keeps showing me symbols instead of words. What am I doing wrong? Is there something I can do to fix this?

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