OKAY this sounds kindof like a problem with object names and groups!
now this is confusing how this works but, heres my idea (im probably way off)
When you get a new object and go to save it in the object maker, which group do you save it under?
Lets say you download a giraffe! everything's working fine and you come to the point where you have to save mr giraffe in an objects group. The issue could be that your saving him under on the of groups that came with the game:
"Default
miscellaneous
my plants
my trees
my rocks"
and so on, now if you do save mr giraffe in one of these groups, then nobody will be able to see him. BUT if you make a custem group, for example:
"African Animals"
anyone that explores your map should be able to see mr giraffe. as long as you send them the exported group file, that would be "African Animals.fho" in this example.
i hope i helped, also i hoped i didn't just say something you already knew.. i tend to do that alot!