I'm using the custom addons folder described by this method ("extra_user_folder"):
My addons folder looks like D:\fs2_extra\
This folder contains various sub folders like \scenery\places, \scenery\images etc.
I'm finding some free DLC file sets do not work when placed in my addons folder, while others do work fine.
If I copy the same files to the location specified by the content creator eg.
C:/program files(x86)/steam/steamapps/common/Aerofly FS 2 Flight Simulator/addons/scenery/usa/places
Then they do work, they just don't work when copied to my extra user folder.
Naturally I've tried different sub folder locations, attempting to match other DLC that does work.
A typical DLC has a folder with some .toc and .tsc files and sub folder called building_textures full of .ttx files. That's about it.
Any ideas what might be going wrong?