make sure to use the MV outside tileset - not MZ (dense forest is currently only available for MV)
i didnt even know the mz tilesets were different. how does the software know when they have the same name?
the software computes a hash value for each file. then this hash value is compared to hash values of known tilesets. if they match the software knows what tileset is being used and loads settings / biomes accordingly.