You've exported the sky right?
I'm really bad at this part, but you can try placing it at different places see if the map maker can find them.
Like
C:\FeralHeart\media\sky
C:\FeralHeart\media\terrains
C:\FeralHeart\media\terrains\mapname
I always thought the exported sky file went into the sky folder and the particles go into the particles folder, though I haven't used these myself yet so I'm not sure, maybe it's capital sensitive as well? Have you looked in the user made tutorials section on the forum yet? I'm sure someone has got a tutorial on how it works. :3